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Les cartes, planches, tableaux, etc., peuvent Stre filmds d des taux de reduction diffdrents. Lorsque le document est trop grand pour §tre reproduit en un seul clich6, il est filmd d partir de I'anple sup6rieur gauche, de gauche d droite, et de haut en bas, en prenant le nombre d'images n^cessaire. Les diagrammes suivants illustrent la mdthode. 22 1 1 2 3 1 2 3 4 5 6 C*^l' .2.^^ : w CO] METEOROLOGICAL SERVICE, DOMINION OF CANADA. INSTRUCTIONS FOR RECORDING RAIN, SNOW, WEATHER AND MISCELLANEOUS PHENOMENA, WITH A SUPPLEMENTARY CHAPTER ON THE TEMPERATURE OF THE AIR. BY G. T. KINGSTON, M.A. SUPERINTENDENT. TORONTO: COPP, CLARK & CO., PRINTERS, 67 & 69 COLBORNE STREET. i S7S. I r s c t F n C t tl P f( fi h r( it ec S S( ii ir INTRODUCTORY REMARKS. A prominent object in Rainfall observations is the determination of the aggregate amount of rain that falls in any district of a country during any period of time. Now, experience shews that the distribution of rain is very partial, one place being often visited by a heavy shower, while another, only a mile or two distant, receives little or none. Hence, as regards short intervals of time, conclusions based on obser- vations at a few points are liable to be very fallacious. In long periods the inequalities may probably to a great extent be balanced; but as far as they are due to permanent local causes, they would be made appa- rent also in the aggregate rainfall in long periods. From what has been stated, it appears that in order that local inequalities, whether due to casual or permanent causes, may be elimi- nated from the results, and correct conclusions may be attained, the stations for rain observations should greatly exceed in number those at which observations of the other elements are necessary; so that for one station where a complete set of observations is made, three or more times daily, the rainfall should be measured at fifty points or more. This pamphlet is designed chiefly to explain the mode of measuring the depth of the rain and snow which falls at any place in successive periods of twenty-four hours as well as in shorter intervals, with the method of registering the observations and of reporting them to the Central Meteorological Office of Canr. 'i ; but it also relates to the regis- tration of the ttjnes when rain and .i.^w falls, as well as the weather that prevailed during each day, and the occurrence of atmospheric phenomena. In order that intending observers who might be willing to devote a few minutes daily to the measurement of the rain, may not be deterred from doing so by the apparently large demand on them implied by the headings of the several columns and the explanations thereon, they are requested to notice that the essential part of the work which they are invited to undertake is tJuit of recording the depth of the rain or snow once each day in the morning, and that at a station which is primarily a Rain Station. Information on the other matters named in the headings of the several columns, although very useful, is to be regarded as of secondary importance. The following list of the other columns, placed in the order of their importance, is given for the general guidance of observers who may be Iv INTRODUCTORY REMARKS. Ind'lw:''''"' ^'^'^""' '^■^°"' the morning .easurccnt of rain (I). Times of bcf-mning and ending of Rain or Snow, (a;. lotal depth of Snow on the ground. (3)- Sleighing. (4). Depth measured at 9 p.m. (S). Duration in hours. (6). Weather and phenomena. As regards the relative importance of the different columns u-ifh respect to the regularity with which the entries are to be m ie " i o be noticed that while an omission in the cohimn donfl, f ™ae. .,,e „,. ,e co„,.„ co.pa,a.lvH. ^^I^J Xtl ;''„:-17; m the other CO unm, do „o. mvalidatc in the »amc dcRrcc tho,c entries tha are made m them; it should be borne in mind, h„.vever thafit I lelt blank, than to make only occasional entries in several Agam, although a full description of the weather on eviry day would be very valuable :t would be better to select one or more conditb's^ phenomena, such as fog, thunder, lightning. Aurora, &c., &c.. and ^o make a po.nt of never failing to record examples of he selected da ° rXt^te^r; tzTj- ^- ^° -- ^ ^- - - -erro:if : REMARKS RELATIVE TO THE SUPPLEMENTARY CHAPTER The general temperature of a district-an important element of its Now, although the temperature is not liable to vary from point to point to an extent comparable in any degree with that noticed in he case " amfall, .t-s requisite, with a view to eliminate the effects of local c'r urn stances, that the stations at which the temperature is observed houTd For this reason thermometers are furnished to a few of the Rain tLtTlu^l"" ''' °'""'^'' ''^ ^^'"'"^ '^ ^^"^^ the additional observT tions with the requisite regularity. ^"scrva It should be understood that these observations, to be of any use should be made with the same regularity as those of rainfall ' In order that the observer may better appreciate the precautions enjoined as to the exposure of thermometers. aTew explanator^ ma k the selected class. ' ^^ °" ""''""''y °«^'°"* '^^ "'^^'^ '« "mited to facts in cment of rain CONTENTS. columns with Tiadc, it is to rain or snow, nal omissions those entries vcr, that it is others being y day would onditions or &c., and to elected class thers only a TER. ;ment of its ious points nnt to point the case of >cal circum- ved should iken of the " the Rain al observa- f any use, precautions y remarks iter. her would be ;d to facts in CHAPTER I._ON THE MEASUREMENT OF RAIN ANF) SNOW. SECTION I. -THE KAIN-OAUOE. The Rainfall expressed by its Depth . (lencral Dencnption of Kain-(iaugo \ arioui forms of Rain-(iaugo Mouths Rain-fJauge used in the Canadian Meteoroloricai Servico Position or Mode of Exfiosing the f iaugo . lo take an Observation with the (iauge Sundry Precautions Hours for Measuring Rain ■■...'..'.'.'..,...', SECTION II.-ON THE MEASUREMENT OF SNOW How the Depth is Measured H£^S:i:u.^:Sir':^":''^;''.^''":*'-^ CHAPTER II.-BRIEF DESCRIPTION OF CERTAIN PHENOMENA. SECTION I.-OPTICAL PHENOMENA. The Rainbow Lunar Rainbow .!..!.!! Lunar and Solar Coronai !....,.. Halos, Parhelia, and Paraaelena ........,...'.'.'.'.','.' SECTION II. -AURORA BOREALIS. Different Forms of Aurora Classification of Auroras CHAPTER III.-NOTATION FOR EXPRESSING WEATHER AND PHENOMENA. Preliminanr Remarks Letters and Symbols to Denote the State' of 'the Weather Symbols to Denote Phenom«n,. "® weather Jimarks on the Letters and SymboU. te! n. ^"*;"?'*y Indicated by Exponent* Sn tt S: ol z a; g- ''"«'^ - •" ^'-''-«- ■ On the Symbols for Fog, Mist, Haze", 4c." .' On the Use of (d) ip), (q), (,,' ' _ _]- On the Letters (- '"casurccl.f '"^ mcasunng glass ,s kept and the rain is est^di:::,^;;,^^^^^;-^:^^^^^^^ ^^ -^^^ ^nche. tenth, and ^-- "P to the 5 inch mad. .; . '^ """ ^''^^'^ ^ cubic inches, fill the the ren,ai,uie, and add to..eth L ' "' """ ^'""'-^ ' ^'^en .neasure the rain tu-icc (il-s the .las': ' t, ! T-^''^?'^^ "-asuranents. Thus, if 4 small divisions, the luol^l^^^^:^ ""''r' ^'^° '^ '^^^ -^ «-'ub,c inches, and the depth r.34 inches " '"'""" °^ -'" - '34 J" using the graduated vessel ]rt ,> f 1 -^ ...... a.. „.. .„. ,. -• - :,i,r. i^XTr:r ■ ^ (7) Sundry Precautions.-Durin.r the fdi r ^ gauge may be covered by a lid s,n„ P r '^'y '"°^^ ^he rain -0.V be in a .../,.>.^ stat^ or if 'k' ^'^^ '"^P"^^" •• "^^'^ '^ ^he probably not remain on the ground t.^i b"'"' V''"' '° ^''^' '^ ^^''^ gauge should be uncovered -xnd.nt ^V"'''"''^ ""' ^"°^^- ^^e rain receives nuist be treated as if it were rab. '' °^ ''"'" ''"^ '"°^^' ^^at it If the gauge be uncovered durin- the fall of I the gauge n,ust be cleared out be?o thf r"L Z '""' T^ '''''^ '^"^^'•^ been overlooked, the whole deoM, / • ^'^""' ' ^^t if this has diminished by one-tenth; o tit dnhf""'"" '^ ^'^ ^'^'^'^^ '"-^^ be tbe gauge was open. ^ ''^ "^ '""^^' ^^at fell on the level while 4 i^-r^^i,!;: r^:^^:;:rr- ;^^ --^'°"^^' — e of that derived fron, snow^hT^h ' 1 ^^^^^^^ ''^' -^^-, except -quently melted, must be treateirl;!^,^:!^;;; ^ ''y '^^^^ -^ -b- -" h^r;tt:t;;::;::^S -j- - ^^ ^-ost be expected, any of waiting for the usuafhotr to 1 rr'"'^ T''""^ '''-^'^>'' '-tcad thejiction^of the ice. "■ '^'" ''^'^^'^^'- '^^o'" being burst by * If rain is acUiMy falling ^"^"Zl";""; ; ran will p.ove ,o l.e more than o ou o fi,, ,7'"''' n' ''"" "" °^— ->'-'P^'tes tlm'^he «auge a clean dry jug or other vessd fo conv i ,f "''" ""■'^■"•' ''^ ^"-'" --' o„ S t ■mngenuMU ,he observer may leave tegj^ " T'" '" '"'"■^ '"' --urement. 4/^1 faJl'nir ra,.-. will I,e lost. ^""^^ '" ^^•"'•k.ng comlition, .and none of ,he nel'y t The measuring glass should never be placed in .he receiver * *"■" '■^^^O'" '•'•''Pi-iined in Art. „, line 4 .hi- T '.'me 4, tins deduction will be rather loo j,.rcat •' fulling* the Tied into tlie ncl the rain is s, tenths, and iches, fill the 'len measure its. Thus, if ' 3 large and rain is 13.4 y table in a lie water. \v the rain but if the tliat it will ^\'. the rain low that it liat enters f this has ■ must be evel while trance of s. except and sub- :ted, any , instead )urst by- es that the out to the • Hy this the new)y IXSTkLXTIONS TO OUSKKVEKS. 5 The measure and second small receiver should be carefully wiped out after each observation, and be kcjjt in a dry place.* (8) Hours for Measuring Rain.-If the observations were equally attamable at all hours, and the convenience of observers could be left out of consideration, the hour to be adopted, when only one observation IS made in the twenty-four hours, would be at the termination of the meteorological day, /. c, at midnight, so that the rain then measured would be that which had fallen during the day then terminated. At those stations, therefore, wiiich include midnight as one of the regular hours for other kinds of observation, a measurement of the rain is made at midnight, in addition to that made at some hour common to all classes of stations. As regards the hour for general use. since a morning hour IS best suited to the great majority of persons, who are then less likely to be absent from home, it is best, on the whole, when one observation only IS taken in the day, to adopt 7 a.m. as the hour for measuring rain. If the observer is willing to make hoo regular measurements of the ram in the day, the time for the second should be 9 p.m.f SECTION II. ON THE MEASUREMENT OP SNOW. (9) In measuring Snow two objects are proposed : (i) To ascertain the average depth of snow which falls on the level in a given time ; and (2) The depth of water to which that snow when melted is equivalent. (10) How the depth is measured.— The most ready method is by means of a rod divided to inches. The measurement should be taken from the surface of the newly-fallen snow to the surface of the ground or (if there was any snow on the ground at the time for measurement on the preceding day) to the surface of the snow that was then on the ground. An experienced observer may estimate the depth fairly without the aid of a rod. It would tend to the preservation of tho apparatus from rust if the observer were to mal enters it is ecual to thar^ltch Tdh " 'h^t:" '!?[ /''^ ^-- nearly true in a fier/ra calw ■ t,„f ff h ''' ^'- ^ '"" "i^y be or the sno. .h^hiuhit u ^ 'i^^^:;:::^^^: ^ ^-"^ p- be asecrtained in- uatchin- the snou- flil-.s .1 M ^ "^^'■'' '''' "^^>' Dismissing this n,cthod a^ .^ZZj^ l^'' ''''''''''''^ "^"^ ^-^■ em])lo)-ed : untrustuoithy, there are two which may be (I) T. General Sir H I fo' r '^ 'T^^;-;'-'--^'^^'---!'-"- Toronto Observatorv. led to the conrl,, T r""''^' ^"■^'-''°'- °^ ^'^^^ ^« -e on the avera^! It 1 1\ ^ ^U, r " ^ l;!::/""^ ^" '^^ as snow var cs in dcnsitv ■ but ;„ f i . '" '^^'^''y ^^ase, assuming i, ,„ be tnc™", J' 1, :":,"'' "'^"'7 °'"«'"'' ^^ {2) The second metliod of findinn- the u-if,.,- ^^ • i "K^Itin. the snow collected by rn^u o an -T'" "' '^.^ ''^'^^-"y ffauof. ^ '"'^ °* "^'^ apparatus called a snozu .0 .l>c „,„,„„ „f the , n!:,;,™|; "' "'""^'^ "■""•' ■''"'°" '■- - -- equal To use tile snow-L\'iu<>-e nlnnn-o ;f ,.. t- n ■ mcncn.nt of ti.e period concerned or till T I "^ "'"■ .round, if no .,„„■ had fallen before .^at pLiod ^^.'^etd """" '"^ S..0.. and rneas„;e';m:;;rfir:td: """"■"' ^"°" ' "■=" '"^ .-. ^"'-"?:rZr.i::':::;:";„fr;'; -^ '-^^y - ^--'^^^-^ p-, average of the results. '"" ""^ '""^ P'"-:^ »■"! take the of ^: rirtr^'c'r t; -ei^t "" ir' "=" °^" «- °" --« .1.^ sn„„. i„ a tal, nal:':::" ■';;-'' ,:"!:f;, " '» t«- - P". to !c.,.,en the evaporating sur- ^vhcre the snow icl the average equivalent.— tliat tlic snow Tin's may be 'y a small part k'aus,'e, as may icii tlic gaufje. 'Vliich may be INSTRrCTIONS TO OliSKRVEKS, 7 face, and pour into it the aitire contents of a vessel cxaclly filled with hot water. Tlie hot water and snow should be then stirred until the snow is all melted, when water should be withdrawn just sufficient to fill the vessel from which the hot water was taken, and the water that remains is then to be measured as if it were rain. (12) Hours for measuring Snow. - The times for measurin.cj the snow should be precisely the same as thuse at which the rain is measured.* hat ten inches ries of exj)eri- ircctor of the n (one to ten) in every case, ccasioncd by thcr methods > by actually Llled a siioiu >pen at both n area equal snow till its to the corn- reaches the tinned iron ; melt the 'ent places, id take the 311 account tter to put ating sur- CH AFTER II. BRIEF DESCRIPTION OF CERTAIN PHENOMENA. SECTION I. OPTICAL PIffiXOMEN'A. (13) The Rainbow.— The rainbow consists of two arches, the lower or primary bow, and the upper or secondary bow, each composed of concentric bands of the prismatic colours, in the order violet, indigo, blue, green, yellow, orange, red,\ which overlap and blend into each other. In the primary bow the violet band is the lowest and the red the highest, whereas in the secondary or upper bow the order is reversed, red being the lowest and violet the highest. The bows are formed by the refraction and reflection of the light from the sun falling on drops of rain in that part of the sky which is most remote from the sun. In forming the primary bow, the ray enters the npper part of the drop, IS reflected internally from the back of the drop, and emerges from the lower part to the spectator's eye. In forming the secondary bow, the ray enters the lower part oi the drop, suffers tw o reflections at the back of the drop, and finally emerges • Snow may be reduced by evaporation or melting, and may sometimes disappear altogethTr before the proper time for measuring it. On this account, and especially in soft weather, when- ever the observer considers that circumstances make it necessary, he should ascertain, to the best of h,s judgment, how much snow fell during different parts of the day, and take the sum of these as the total fall. + The order of the colours may be remembered by the word viiiOYOR, which is formed from the imtial letters of their several names. 8 '"STklciroNs TO -.i,s.;rvers. Tl " " '" >"-' >"i tlif horizon. '°"'""'' ^■^t'^Pt M sunset, when on^:^,,;^;^ "'■="'"" of "- Primary bow . 43", anc, ,ha. ^ ^^^ n. h„n»„, co„„„e.e ,e„,,,„^^ ^^ ^^,,_ ^^^^^ ^^^ 'f the sun has an altitude less than .-,• h„„ ^ . 'f '"e 3un. altitude be be.„.e. 1 ' ""^ "'^ ^ '-"• "' "- ""' S3 ■ "■= «co„dao- bow only If «.e sun. hl,net than 53; neither bow can be seen. ^cpre..:d;T„: tnirbe";::,'^^'^:' Z'™' '■■■^ ^"■'"^ '-•- -i.. Be ^- '- '- - -- -.. ".r,. :- iXxtui" (14) Lunar Rainbow— R;,mK 'noon in cvactly the s.:nc r^^Z]^^,^'^^' '^ '^'^ ''S'^^ of the -n, which is vc-y n-u-cly, th ^ a;e of^ " f ' "' ^'" ^"" '^ ^ut .hen The centre of a Lunar Rainbow n'ust be .t' -^ ^'^•""^^' appearance, opposite to the centre of the moon ' ^'°'"^ '" '^'^' ^J^T exactly (15) Lunar and Solar Coronas t coloured rings round the moon Som^ '°'"°"'' '°"^'^* ^^ ^^intly once, the diameter of the second bei . f '"° ^'^ "^^^ -^ -en at th.rd three times the diameter of the ^ I"' "'^I^ ^-'"eter of the >ntcT,or ring varies from 2° to 4° l" .7 ^^^ ^^'' ^'''"'''^' of the border and the violet on the inner" '^^ ""^ ^^" ''^^ '"^ °" the outer ;^-^ b:°;c:; :?^- r->:^ -- - on account of the through coloured glass. ^^ ^^ ""^^^ visible by viewing it ''^^^^^^.T^::z^-;^:::^ ;7 -. eirce. I 'er ot 92 , and which are seldom y INSTRUCTIONS TO OUSKRVF.RS. s owing to the loss secondary bow is vactly opposite to 't at sunset, when 'V is 42", and tiiat 9 seen together. ll,e colours arc feeble, especially that of the larger which ,.s almost or quite white. The lart,^er is very uncommon. Where they exh.b.t prismatic colours, which is rarely the case, the red is on the tHstiie. Sometimes the halo Is intensified into two bright spots, one on each ^e of the central luminary. These are called Purhdiu or Parasciauc (mock suns or mock moonsj. ■duced : ' both bows may y be seen, ndary bow only Horizon will be r portion of a of the ground. e light of the un; but when \' appearance. - sky exactly iist of faintly - are seen at meter of the meter of the on the outer ount of the y viewing it irge circle^ are seldom SFXTION n. AlTli(lI!A HOltKAMS (17) Different forms Of Aurora. -The Aurora Borealis presents Itself under six different forms. ^(i) Aurora/ Twilisht.-h light in the north, resembling,' the dawn of {2) Archcs.~Kxz^, or circles, or zones, formed at various altitudes, usually between N.E. and N.VV., being sometimes the mere boundary of a segment at other times a dense pillar of light forming a grand columnar arch, which spans the heavens from East to West. It frequently moves from North to bouth, usually advancing but little further than the Zenith. (3) Streamers.~-^\,^r^ spindles, usually shooting up from an arch, or from a dark smoky cloud, which lies along the northern horizon, or rises a tew degrees above it. (4) Ct;mw.-A circular zone round the pole of the dippin- needle ie the point m the; sky towards which the elevated end of the dinpin- needle is directed. This point for Toronto is about 15° south from the Zenith but vanes in position at other places. The corona is formed of wreaths 01 auroral vapour, either white or of various prismatic colours with streamers radiating from the circumference. (5) f^W.— Undulations which commcfnly flow upwards towards the centre of the corona, along the line of the streamers, but sometimes course along the line of an arch from East to West. (6) Auroral Clouds.-K milky, vapoury bank in the North, the quan- tity and apparent depth of which afford a prognostic of the intensity of the commg aurora. (18) Classification of Auroras.-From the preceding varieties it will be found convenient to arrange auroras in four classes. to INSTKt/CTlONS TO (#BSR«VERS. «W«»». and wavM. ' ""^ '°""' "'""■•'>■• "clio, streamer,. eie£rs;rl";r?:r'rTrd;t°';lr"r''''° "■"" '"= cl,araeter«,i„. CHAPTER III. NOTATION FOR EXPRESSING WEATHER AND PHENOMENA. ^onLl^'^^^Zs^Z'^^^^^^^ ^^t^e aqueous is commonly called the -'sT;t of \h T^' P""' ^°"«titute what resulting from those modifications o "? ""' "" ''^ appearances phenomena" is applied .Tso ' H ?, ''' ''^^ '''"" "atmospheric ticable in every caTe to a " ^e^^^^^^^^ ""'"^^f ^^^^ '^ - -^ prac- niade in t:,^ fbHovvin. listZlfth^ f J"'"^"' ''"''• "^^^ reparation arbitrary. Some of fl eTms ed ^'d ^ ■'"'^' *° ^^"^^ ^^^^ - weather might with ^JZp^yV:::;'T::T ''''-' '' ''^ others are applicable not so* much .n Fu Phenomena, while weather ofwhich it is deslaTlerL:;::"':^^ " ''''^'^ ^^ ^' -ytl-ri°Ld ^eS'hlTtterr 7^'. f ''' '^--^ P'^— a -symbols. Th.. ^tte^s belon, mo r I ''P'^'*^'' °^ '^>' <^°"ventional by Admiral Be., -^ -^ Z "^ 1° f '^^^'^"^ °^"°^'-^^-" -Produced mended by the V,, ', ,-on , 'ss 71^7 ^ "n rT''"" ^^^'^^ '''-"^- necessary to sur.).>'' . .i-,. :^f\u^ , ,/^^" " ^^^' however, been found and also to intro'-iu,. c: u Iv symbols "' '' '^P'^'' ^^""^ ^^ 'y"'^''^'' ?ast fhree out of :hes, streamers, aracteristics of :Iiaractcristics, but without a aurora of the ' form of the AND he aqueous stitute what appearances itmospheric is not prac- • separation e extent as ates c'i fhe lena, whilo T effi '' of )henomena nventional introduced se recom- een found '• symbols, INSTRUCTIONS TO OBSERVERS || (20) Letters and Symbols to denote the State of the Weather. Lkitin. SvMauL. b Blue sky. c Cloudy, but detached opening clouds. t ® Overc.-ist, the whole sky being covered with imper.-ious cloud t © Clearing weather. d Drizzling rain. f Foggy. t ^AW Misty ; i.e., haiy, caused by condensed vapour alofu 00 Dust haze, or hazy from dust. t fi Smoke. g Gloomy, dark weather. h A Hail. A Soft hiiil. I < Lightning. P Passing temporary showers. 9 Squally. r • Rain ; i.e., continued rain. s * Snow. \ I Flurries of snow. -* Ice crystals. t* Snow drift. t Thunder, n: Thunderstorm. u " Ugly." Threatening appearance. }• Q Visibility of distant terrestrial objects, whether the skv be w cloudy or not. Dew. Hoar frost. Silver thaw. Glazed frost. Strong wind. In the above list the new symbols not included in those recommended at the Vienna Conference are those which express " Overcast," " Clear- ing weather," " Misty from condensed vapour," " Smoke," " Flurries of snow." and "Visibility of distant objects," They arc indicated by f on the left of the column. V 11 '''^T^<^''riOXs TO OiiSERVKRS. (21) Symbols to denote Phenomena. O GJ Solar Corona. Solar Halo. Lunar Corona. Lunar Halo. Rainbow. Aurora. snow. • ''""'"• ^'^"^' *° means light snow ; ^2 heavy dunng dayhght is ordinarily ^/:. tl e I f/^ ? °''" ^''"'^""^^ ^ ^'^^^^'^ ^^7 the sky is clear at night, or vv enever " ^ ^ "'^ ""^'^ ""' "^^^ ^^'^^^n not blue, is clear. ^"^ ^^^-"^ve, f.on. any cause the sky, though (^) followed by (c) dermfpc fi, clea.- part of the'slt^ be^g g. t^^rr ^' VT '"^^'^^^ ^'-^^. ^^e If the clearness of the si K " "^ '"' ^'"^ '^ "^'^^^^J- (^) should be followed by tl "i ''bZ^'t '^' '"^^ °^ ^-°'<'-"- the letter -"sed vapour, or that I cL:^;;;::'^;i^-x;t ^^^f ' '^' - bulif is^lr:;:::::::;^-;;^^-^ ::-^^ ^^^^'^ ^^-^ ^Paces intervening . part that is clear. "^ ' ''""^>' ^^^'"^ ^'^ ^he sky should exceed the . (2^^ ^ o'- -^ to denote fog. These u-^ f . k 's completely surrounded by foke, the letter ""St, i.e., con- >ke. intervening; d exceed the he spectator le exponent onsisting of ness of the nail drops, or passing showers, shews that the rain falls in fregucnt showers of short duration which while they last, may be either heavy or light. These are exem-' phfied by what are commonly called " April showers." The letter {r) in the weather column indicates the fact that rain is falling, without implying that the drops were exceptionally small, as in a drizzle, and also that the fall is fairly continuous, i.e., not frequently interrupted ; but (.) does not necessarily express rain of long duration (- flurries may be expressed by applying the exponents fo) and (2). (30) Ice ajx/a/j.— These arc minute crystals of ice that are occasion- ally seen apparently floating in the air, and glistening in the sun's rays Ihey are chiefly observed during bright weather wiUi hard frost. (31) " Visibility of distant objectsr~1\xx^ term has no reference to the clearness of the sky, as the condition which it expresses may exist whether the sky be cloudy or not, and is most frequent when the general character of the sky is threatening. It often occurs also between heavy rain showers. The symbol used above for "visibility" has been sub- stituted for V, on account of the resemblance of the latter to that adopted for " silver thaw " by the Vienna Congress. ( \ H (32) LiVhtnin INSTRUCTIONS TO OBSKRVKKS. frcezmj,, tlK-rcon. It differs from ■ r ., "" /"'"'"B '-""I immediately latter i,, r„r„,ed by the c ndenLr "f " ""' '"'""''■ "»' "-^ no. the sa,„e sn,„„[h surface " °' "''"""• '"^ ""-Ifently has I' I , CHAPTER IV. REGISTRATION OF THE OBSERVATIONS. SECTION I. KKCORO O. ..CTS K^.TH. TO THK ST.TZO. ... .pp,,,,,, ^^J'l^^::i2^:^r' ^o. meteorological observations position, elevatio and 2 "!,''" ''''''' ^^^^'■- ^y the geographical station is placed on the no > ^'"''^r'''' ^^ ^'^^ district in which the pics ; on L ^i'.z:': ::z:::^^T r '"^ ''- ''^'-^ -- and on the qualit>^ and n.ode o 1'^^^^^^^^^^^^ ^'''^ '^"^'^ ' v-ieu- of preserving at the various st.M '"'^truments. With a descriptive of the dist "ct Ten is r'T"™""""' ''"""'■^ °' ^'^^ ^^^^ supplied to each station, beann" 1 ' til ?t1""'"' ' '''''''' '^""'^ '^ to Station and Appa.vtu "^ At h '" °' ^^^^^ ^^'^*>^« directions are given relativt to fhnf I '"''^-'""'"8^°^ ^his book detailed of entering them '^' '^"^'^ '° ^^ '^"^'^'"'^d. -"^ the manner SECTION II (35) Headina: of Pflo-p p.,^ also the names ff the sSi,;:!i";;";:."':_'"'«:, «■.•-■ "'°""' ="" >'="■ • — ^"V) proviot-c and oDServer. INSTRL'CTIONS TO OHSERVERS. 15 et lightning or of isturc on trees or 1 after great cold. i surface formed nd immediately fespect, that the onsequently has DxNS. ?PARATUS. I observations geographical ; in which the ■ station occu- ns are taken ; nts. With a s of the facts ster book is ^CTS relative ook detailed the manner . WEATHER 1 and year, Columns headed " Rain" (36) •• Times of Beginning and Ending," &c.-In the first two columns write the times at which, or the hours between which, the first rain began and the last rain ended ; such beginning and ending being between the midnight which began and the midnight which ended the actual meteorological day, i.e., the ordinary civil day. If the rain continued from the previous day through the midnight which began the day, the time of beginning should be written " through o'>a," or "thr. o'' a ;" and if the rain continued past the midnight which ended the day, the time of ending should be written "throurrh mid'" or "thr. midV '^ If the time of beginning be not known within an hour, the hours between which the beginning was known to have occurred should be written. Thus, if it began between midnight and 5 a.m., the entry should be o a Similar remarks are applicable to the time of ending. In the c6lumn " Duration in hours " should be given the total number of hours during which, to the best of tlie observer's knowledge, rain was actually falling. Columns /or Snow. (37) "Times of Beginning," &C.-The entries in these columns are to be made in a manner precisely similar to that described fo- the corresponding rain columns. Column for Depth at Morning Observation. (38) Depth of Rain.~The depth of rain measured at the time for the morning observation should be entered for the day in which it was measured,* without reference to the times between which it may have fallen. Thus, the rain measured at 7 a.m. on the loth of the month is to be entered on a line with the loth, whether the rain actually fell on the loth or during some part of the 9th. The gauge should always be examined at the regular hour for obser- vation, whether the observer supposed that rain had fallen or not. If no appreciable rain was found in the gauge at the proper time for measuring it, and the observer was aware that some rain had fallen since • If the observer should hare taken one or more extra observations or n^a™eni7towee"i^ two consecutive regular observation hours, the depth fn.ind at =uch intermedi.it,- .-.r extra obser vations should be added to the depth measured at the next regular hour. (See note to Artl ) i6 INSTRUCTIONS TO OBSERVERS. the time for the previous rain observation, he should enter the letter (r) for the depth alien ; but if he had no reason to suppose that rain had talien, he should leave the place Mr/d-. r39) Depth of Snow to 7 a.m.-Thc depth of snow to be entered for the morn.ny hour ^ a.m.J is the total depth that fell between the previous regular observation hour up to 7 a.m. This depth will usually be that measured at 7 a.m. ; but in soft weather, or whenever there is a danger that the snow would disappear or be diminished if its measure- ment were postponed until the regular time for the observation, the observer should measure or estimate the depth of the snow that fell in different parts of the period, and enter the number found by adding ogether the several partial depths. This sum, supposing the estimation to luve been correctly made, will be the same as the total depth which would have been made at 7 a.m., if none of the snow had disappeared, (bee note to Art. 12.) If the snow which fell be insufficient to whiten the ground, the letter {s) should be written for the depth. 40 Column "Melted Snow." sometimes called " WW Eguiva- /r«A -If the observer is furnished with a snow-gauge, he should enter n this column the depth of water obtained by melting the snow ; but if he IS not furnished with a snow-gauge, the column is to be left blank. TJ;°^fT '"^""^^^ Precipitation." sometimes written "Ram and Melted Snow: -X\,^ entry to be made here will be the number found by adding together the "water equivalent" (if tiie preceding column be used) and the depth of rain. If the preceding column be blank, one-tenth of the depth of snow (not melted), as an approximate water equivalent (see Art. 11), should be added to the depth of the rain. Example : If the depth of rain be 0.37 inches, and the depth of snow 3.2 inches, the approximate depth of water equivalent to the snow is o X2 inches, and the total precipitation 0.69 inches. Depth at Night Observation. (42) If the rain and snow be measured tiviee in the 24 hours the second observation should be at 9 p.m., when the practice to be followed will be precisely the same as that at the morning observation. It is desirable that the observation be made every night as well as every morning; but if the observer does not measure the rain syte- matually .v.ry night, but does so on special occasions only, he should in ' ^ « >»m l Iter the letter (r) se that rain had o\v to be entered fell between the cpth will usually lenever there is a d if its measure- observation, the ^now that fell in bund by adding g the estimation >tal depth which lad disappeared. round, the letter Water Equiva- he should enter he snow ; but if be left blank. written "Rain be the number the preceding ding column be an approxirrate 5pth of the rain, : depth of snow ;he snow is 0.32 : 24 hours, the : to be followed ition. light as well as the rain syte- \y, he should in INSTRUCTIONS TO OBSERVERS. 17 every such case enter the depth found at 9 p.m. He should enter the rain as 0.0 when he examines the gauge at 9 p.m. and finds that no rain had fallen, and leave the column blank whenever lie failed to examine the gauge at 9 p.m. (43) If the rain be systematically measured at 9 p.m., as well as at 7 a.m., the column for 9 .;.m. is to be left blank whenever, on examining the gauge, no rain is found in it. (44) If the observer does not usually make an observation at 9 p.m., he is requested to do so on the last night of each month. He is also requested to enter the observation of rain for the first of the month at the foot of the page for month just completed, as well as at the top of the page for the new month. (45) The remarks made in Articles 42, 43, 44, are applicable also to the record of snow up to 9 p.m. (46) Column " SleigMng."-This column is to contain one of the figures o, I, 2, to denote the general state of the roads in the neighbour- hood of the station, (o) representing no sleighing, (i) bad, and (2) good. If sleighing is interrupted during its ordinary season, the entry should be (o) ; but when sleighing is completely at an end, the column may be left blank. (47) Column " Total depth of Snow on Ground "-This column is to contain the total depth remaining op the ground, as distinct from that which fell in the interval between two consecutive observations. This would be equal to the sum of all the previous falls in the season, if no causes of diminution existed ; but as the depth is reduced by com- pression, and by the waste attendant on evaporation and melting, the actual depth remaining at any time is usually very much less than the said sum or aggregate. It would be ufficient if this total depth were entered once or twice a week (say Mondays and Thursdays), the approximate depth in inches being given for the woods or open field as well as for the high road ; the entries being made thus : "woods 20" or " field 20,' and " road 8." (48) Compartment " General State of the Weather." — In describing the state of the weather the observer is at liberty to use words instead of symbols,* provided that there be sufficient space. * The term "symbol " is taken to include letters. IS INSTRUCTIONS TO OBSERVERS. :r'i- If two or more symbols are used to describe en .^.t^ , .- • cond.t.ons that are present at the samel^^e thH-'ld h'°"' '"' down without stops between them • h„f ;f v • ., ^^ ^^ ^'"'"en dftfons at different parts :rthe Ih^Ic pe Ld r.^h" h1h° '''"''^ ^- i-s provided, the symbols or trrouns of sv^hnl °' "^ ^' ^^'^P^rtmcnt which follow in succession arrtobrv^.T- ' "^ '''^''''''' conditions colons (;) between them ""'" '" °''^^'- ^^ ^ime with semi- li would add to the value of the description if fJ, k • • ending of the time to which each svmhnT begmnmg and This may be done by writing t^Te time of L" ^""^ ''''''' '^^'^ S'-"' time of ending on the rZ of Z k f ""'"^ °" '^'' ^''^'' ^"^ the semicolons. " ' °^ '''' ■''^""'^°' °' ^^--o"?- and within the ano';;Tr.LTartlt::nvh:ch^^-^^^^-^^^^^^ '^- -^ -^^tion to definitely stated ; or rmavbth.^T"" '^°"''^'°" ^^S'- cannot be observer. I„ either suc^case thl K ^""" ''"^^ '^ ""'^"°-" ^^ the beginning by writing down hhotHr "^^ T-^r ^''^ ^^^ ^^ occurred, in the form' of a "fractn the elr;;;: 'le' ''^ '^^^""''"^ - s^2^t^=? -r ^- ^ J^X2g^::::i dimmed by mist, fhe modeVieJclr;;; ItlVr ^.^^ f^^ -^^- oftair^'^tl^rnTitedT ^^^^^' -^"^ those descriptive as. for instance'when ^^:::l^i:^ :Z:r^- " ^'^"°--^' rare or of very short -lurafinn ^ , , "^"^ referred to is comparatively event than of a ..J or conZr ".^ ""T °' ^'^ ^^^'■^^^^'- -' -" Pheric conditions are described ' " ''' '^"'^ °' "^^^^ ^*"^°- obS:.^Ss;m^^'A;:'2' ^^^r^ " ^^^ ^^--^°" °^ ^^« for phenomena : ' '° "^^^ ^' transferred to the column Hail; Thunder or lightning of short duration • Dew, hoar frost, silver thaw, glazed frost, ice crystals. When the symbol for strong wind is used fl,. ^- ,• c , may be shewn by the position T.f^I, ' ? ''''^''^'^ ^'^ *^^ ^^'"^ ^l conditions, i.e., hould be written i to describe con- tlie compartment >resent conditions time with semi- ; beginning and lates were given. the left, and the and within the 3ne condition to ■gins cannot be unknown to the ss the time of the beginning ng uppermost, ling between 6 )lue sky rather 1 2 ) • as the columns 5se descriptive phenomena, :omparatively laracter of an ertain atmos- retion of the the column INSTRUCTIONS TO OBSERVERS. 19 lis. of the wind >eing upper- , and so on. (49) Direction and Force of the Wind.— It is not expected that observers who use this form should keep a systematic record of the wind ; but if any observer is willing to do so, he should rule in the com- partment of " Remarks " a column for 7 a.m. and also one for 9 p.m., if the rain is measured at the latter hour, and enter therein the direction* from which the wind was blowing, at the time of observation, to the nearest of the eight points, with the words "light," "moderate," "fresh," " strong," &c., to e.xpress its force. (50) Column "Phenomena and Time of Occurrence."— Enter in this column the symbols that express any phenomenon that occurred during the twenty-four hours, and indicate the time when it occurred, or the times between which it occurred, in the manner explained in Art. 48. It will be necessary, however, to affix the letters (a) or (p), for a.m. or p.m., to the figures that represent the time. If an aurora is recorded, the class, according to Art. 18, should be given ; the number of the class in Roman numerals being written under the aurora symbol. (51) Column or Compartment " Remarks." — The following details should be entered in this compartment : (i) Notices regarding instruments and observation, such as a breakage, a change of instrument, change of position, or a change in the time of the observation. If an observation be accidentally taken before or after the proper time, the fact should be stated in the Remarks. (2) Notices regarding any phenomenon for which there is not sufficient space in the preceding column, with a reference to the place where a more detailed description is given, when such is thought necessary. (3) Periodical events connected with the progress of the season, such as the following : (a) First snow, or frost, or sleighing ; ice formed or broken up ; open- ing and closing of navigation ; mill work begun or stopped ; Indian summer, &c. {b) Appearance or departure of migratory birds, first croaking of frogs, &c. {c) Budding and flowering of plants, maturity of fruits, &c. * The true and not the compass direction should always be given. 30 'NSTRUCTIONS TO OUSERVERS. SECTrON III. ^52. Pnf . """'' "'^'^^'O^^f^^GI^'AL RETURNS. daily register book. The renorK or T ^ """ "^"'"^ '" his the Central Office are to be eCrTn "" !™'"'"''"<=d monthly to ■"».!. fe eo,„,„e.e,, ,„, ,„„. l, X'e '■' r *"""■ ^' »"" -'"= ong.nal in „,, b„„|,, ,., ,„ f„ , ;rd ,| h •,"""'"'''""' "'■"■ «■■= Supermtcndent, Meteorologiea, Office ^L'L""' "'""■""' '^ "T'- The report mav h. • , , '"""= '^^'Utions. w.th the ends not inclosed. Th'Ztf^n '" ' °" '™' P"'"" "■'''ppr; -y matter in the nature of a I , " tS „" '""'"" """ "»' "«'■" no. forn, part of the report „„s. be trTttenlX"?:™"'™ '"" "- the register book and T^', reLrns ""''' *°"''' '='= °''-™'^d ^ik "„ (0 Vulgar fractions are nnf f^ k Th„s,te„andal,airsho„ldb:^:»t:::r5:^„t.Tol' ^'""°"""'>'- f'^mb-'rr-pirrr^^^^^ places be wanting, its place shon'n .^'"'^ '" °"^ ^^ the decimal =-.'.. .o be entefcd ^^C^^^^l ^X'^l.-Vltl"™-" :i::--^ - -er entnes are not .rongX;:; Z. r^t hat? ^- "en::^r°bV'S,':i:,r"^n^' "= "'^^ '^""^ '' -"'^ written for it. ^^''"^- On no account should (o) be (4) When the observations taken at th. consecutive days, are identical thr.n. f '"^ ^°"''' °" ^^^'^ O'" "^ore occasion. On no account ho 'id " T"Z T ■ '^ "^^^^^^ «" -^h o^a^dash^o^ny other sign. ^'"''°" ^'^ '"^''^^^^d by a blank, • Tivo persons should be emr'^'TrTiy; ~: — __ ' ' ' '" "" '^°'"p«"-"' ^^-oo. one shouiT;;:;^^,;;;^- y Register.— observer in his ;d monthly to '^s soon as the ison* with the .iscd to "Xhg INSTRUCTIONS TO OUSERVERS. 2I (S; Figures, letters. &c., should be written in a plain, distinct manner. xvithout flourishes, so as to be read without danger of mistakes. (64) Conjectural Entries to be strictly avoided. -It is par- ticularly requested that if an observation be accidentally omitted no attempt be made to fill it up by conjecture, and that the observer strictly enters what he actually observes, however unlikely the observation may seem. ^ same rate as ditions. cent stamp, >stal wrapper t not contain 3n that does iding Am- ved alike in •Ctions only. de with the :he decimal areover, (o) T >• •47, .6 0-47, 0.60 ; to lead to - it would ild (o) be 3 or more I on each ' a blank, aiout). CHAPTER V. MISCELLANEOUS MEMORANDA. (55) Packing Cases to be prt,served. - When an instrument is received at a station, the packing case, with its lid, is to be carefully preserved in a clean, dry place, and is not to be used for any but its proper purpose, so that it may be available in the event of its being needed for returning the instrument, or for transferring it elsewhere. (56) Damaged Instruments not to be returned without In- Structions.-When an instrument is injured, or is supposed to be injured, it is not to be returned to the Central Office, or sent elsewhere for repair, without instructions to that effect. When a damage or defect, real or supposed, has been discovered the fact should be reported to the Central Office on Form 26. This report may be inclosed with the next regular report, if the latter be due within three days, or with a letter, if the observer should have occasion to write on other business ; but in other cases the report may be sent by mail in a one cent opeti envelope. (57) Reports on Instruments, &c., to be on Separate Papers. -Any report to the Central Office of damage to an instrument, or of change in its position, or of circumstances affi.'cting its exposure or alteration in the time of observing with it, or remarks as to its mode of working, with suggestions for its improvement, should be transmitted on Form 26, as explained in Art. 56. f ' I I I '■ I 'I ! 22 INSTRUCTIONS To OIlSERVHRs. (68) Requisitions to be on Soeoial Pn-^. r, . . Co„tral Office ,,., instruments r.;rf„,T/,M "'''''''•'''"= '° ">. W. b„t ,„ Written on a ^;, :/;„;,:";; '"" '"'"' /-' '/ a rcq,n..,„„ f„„„, „ „„ ,„^„ „" Loa'!',J?S!orrHo"4'-A: „r.L^r ^ '-» ^ station o„ mcnt tl,c property of the L,„l„„o7can; '';,';, T '""" "" '■'"™- another station without definite instructron" f™, l"r '"'"f" " '° oven though he- may not (a, he suonoscTh! *,'= Central Office, such action defeat, the our ,„.. f r , ^, ''' """' '"' ''' ''"'"'^If. as furnished to hi,n one o * ," ht T "''''"'•°"" '"""""™' "- observations by accidents lo lltl't^^^ l^"*^ ■"^' "« ^PP^S^' of .be .ocim'yTvhtd::;^;:::";"::; tr r"-' ""-" '- » ^'-^'^ .he case to the cent;:, ost ;;r r^X^z^d tr':' ■■'''. rr proposed station with instruments intended for his o„„ Z. ' ""= (80) Blank Poms to bo Carefully PreserTOd ni, requested to keep all articles of st«;„„ '"''"'"•-Observers are ™ions in a sa. p^and ^L^^^siSr;;!:''--- enSet''tL°f.udrom°e? "f «»»'»8y-Observer3 who desire to more'of the folTowfnf J!rt!"'°''' "' "-"'"-^^^ 'o consul, one or Buchan, A. Handy liook on Meteorology. Herschell, Sir John. Meteorology. Loomis, Professor E. Treatise on Meteorolo^ Scott, R. H. Weather Charts and Storm Wa rnings. ill' [23] jisitions to the inn part of a 11 some other r. hen necessary, Station on m an instni- transfer it to -■ntral Office, it himself, as itriiment was ppaye of the fi a suitable i'OMld report furnish the •servers are I the obser- to diminish ' desire to isult one or CHAPTER VI.— SUPPLEMENTARY. ON THERMOMETERS, AND THE MANNER OF EMPLOYING THEM FOR THE REGISTRATION OF THE TEMPERA- TURE OF THE AIR. SECTION I. ON ORDINARY MKliCl'IlIAL TIIKHMOMCTEKS AND CKUTAIN I'ROI'ERTIES OF HOOIES IN RKLATION To HEAT. (62) Measure of Temperature.— To measure changes of tempera- ture recourse is had to an easily recognized and easily measured effect of changes of temperature, namely, the e.\pansion which Is found to take place in most bodies on the application of additional heat ; but as expansion differs in different substances, it is requisite that some one substance should be chosen for this purpose. An instrument furnished with a contrivance for measuring the expansion or contraction whicii accompanies changes of temperature in the substance chosen as a standard, is called a thermometer. Mercury is the substance ordinarily used as a standard of reference for the construction of thermometers, chiefly because the apparent* increase to the volume of mercury inclosed in a glass tube is propor- tionalf to the increase of its temperature as measured on rigid principles, so that apparently equal additions to the volume of the mercury indicate equal additions to its temperature. (63) The Mercurial Thermometer.— This instrument consists of a glass tube or stem with a fine or capillary bore, as nearly as possible uniform throughout, with a bulb at one end, whose capacity is largely in excess of that of the bore. The bulb and part of the stem are filled with mercury, and marks are placed on the stem to indicate the expan- sion and contraction caused by changes of temperature. Before the mercury is introduced into the tube, the tube is calibrated that is, it is ascertained that the bore is of uniform calibre, or that its cross sections are throughout of uniform area ; and if not uniform, the * The actual is not identical with the apparent increase, on account of the expansion of the glass. tThe proportionality is not absolutely perfect; but the error oceasionetl by regarding it a» »uch is too minute to be worthy of consideration. I ii is if ii 24 INSTRUCTIONS TO OIl.SKRVKRS. extent of the variations in calibre at cliffc-rent n.rts Tl • >u necessary i,, order tjiat equal length, in m / '"' ^^'"hration is k..ow„ relation ,„ „,, interval be.l'-en Z, "-"'''"■""'= ■"=>• >■••"'' » po"^i!:::^^;Lti,;;-:;:L'zirr;"'"^^r'''- The part of the tube intervening between fl,. r • points is divided into i8o oirts r.L ! '"'^"'"^ ^"^^ boiling are called " de.M-ees " Ii thn h ''^':'^'^" '"^ ^^'^^'^ ^'oiumes, which parts graduation for the varying cap^cit^o; the Lri""" '^ '"^'^ '" ^^^ The graduation should be continued below xh. r ■ sometimes above the boiling point by etth ^0^ T"'^ '^"'"'' ^"^ representing volumes equal o fhn k ^ °" ^''^ "'^"^ P^i-tions points. In Fahrenheit's' c.le as r f ''' ^-"ing and boiling foUows that the point 3V '^;-^-^-^^^^^ point is marked sAit o\ or, as it is called zero also T ^'"^ P°'"' '""-'** ^^^ "^^''ked called ten degrees beloTz'eron ^'^'^P^^^^^'''^ ^-" ^^i^'rees colder is The graduation fLtrcirjesshTlLT';^:!'''' '' ^^'""^" --• but it is useless to extenHTtf , . ^''"'^ '^°'^'" *° "^^''ly -40"; at -3;".9. ''"^^"' ^^em lower, because mercury becomes solid term'-ftSr;? ^^^^^3.^?^^^^^^ Thermometers.--The besides being of supeWor ull^ ! "' '° ^ thermometer which. correspondence of ri;te;afre::'''r^^P" '' '^^^^'^ ^^e' of n^ercury, is graduatd^o^ above' h' k ',-""°"^ ^° ^^"^' -'"'"es freezing point. ^°'' '^^'^ ^°'^'"g P^'nt to below the In a standard the correctness nf fi,„ 1 -i- freezing point, can be verified bvdirt ^^ ^"^ ^""'' '' "'" ^^ ""' '"^^ to any other thermometer ^ experiment, without reference I - "Jli- fl lH^M.',. INSTRUCTIONS TO OUSERVEKS. calibration is ury may cor- ■nipcrature. ^tcrmine two - may have a the melting of these has tcr constant r-'ahronhcit's and written s a certain antl boiling vhich parts the degrees ade in the point, and n portions nd boiling ved 32°, it 3e marked colder \i ;en — 10°. •iy-40°; 'mes solid rs.— The :r which, ards the volumes -low the s of the eference 25 As th^': chief use of a standard is to test other thermometers, its range should extend each way as far as those of any thermometers to be compared with it; and as these arc wanted sometimes for very cold climates, it i;; better to extend the graduations to the point where mercury becomes solid ( — 37".9). Thermometers for meteorological purposes commonly have their graduations extending not much higher than 100°, unless they a.e designed for very hot climates. (65) Change in the Position of the Freezing Point.— If a thcrnjometer is graduated soon after filling, i.e., soon after the glass has been subjected to a very strong heat, and has been thus unduly expanded, it will afterwards, by its contraction, furce the mercury up the tube, it may be from \° to 2°, and cause the true freezing point to rise by that amount above the mark 32". For this reason a thermometer ought not to be graduated until several months after it has been filled ; but even when this precaution has been used, there will often, in the course of several years, be a slow progressive contraction of the bulb and a consequent rise of the freezing point, necessitating the subtraction of a correction throughout the scale, which will increase from time to time, and finally become constant. (66) Index Corrections and Rules for applying them.— Owing to the difficulty of making tubes of equable bores, and the loss sustained by rejecting those whose bores are not equable, thermometers are often sold having not only large errors, but errors varying consider- ably at different parts of their scales. On this account thermometers should not be used until their "index corrections," or the corrections to be applied at dilTerent parts of their scales, have been ascertained by comparison with a standard. It is a practice among English makers to supply to purchasers certified copies of the index corrections of their thermometers. Of late years thermometers certified by the Observatory of the Royal Society at Kew, arc examined as low as the freezing point of mercury ( — 37'-9)- Those which have not been thus tested ought not to be accepted, however correct they may be at ordinary temperatures, as it not unfrequently happens that thermometers, whose errors above 32" do not exceed o°.2, are in error 4° or more at or below zero. The thermometers employed in the Meleurological Service of the Pominion of Canada are first compared at Kew ; they are again com- 26 JNSTKLCTK.X.s Tu OiJSERVERS. change, to „..„,„ ,„,, „„, js^b:;::,,.;;";^':. '""''^ ^^^'-^^ "■= -owe. .„„ .,e ,...,,ri^:t:r„i; r Ja 'i\rr---= folIti,™'r "" "'■'^'^'■"^ '■"''^■•■' =-™'-'. »■>.->. cover., all cases, is .h. con-cco. .cadin, „,,, be „.e s„. .Ith ihf f„lo':°,':°"""' ""' '"= + 'a'nd :;r:;;:e^ i"^^™ r^'^^r '''- """-^ ^^^-^ °- ^^'-"^ frrea.er. and the co/rected " din /'"n k' T'^' °' *' "™ '''"' 'h= -b.ae.i„„, „,, .„. retni: r.'of 111: ^^r °''"'"^^ '^ '-' 46°.6 -120.5 - o°8 + i°.o 4S°8 -ii°.5 ^4 -o°.6 -i°2 4-2°0 Examples : Observed thermometer readings t.. so°.4 - ,0° , Index corrections _r^o \,'^ Corrected thermometer 'readings;; ..'o'c 1 Si Index correction papers arc tntdo r ^^ '^ " "°'^ ^""^ °"-« shorter intervals, according as he dnt"' J ''""^^'^'^^^^ ^^ longer or fro. temperature to tet^^ptrrtu!; t ^ o'r". t^ ^l^^f °"j ''" ^^-^'"^ for two temperatures consecutivciv ..l . , "'^''•^ correcdons more than o°.i, the correc o' f^ ^ -^ '" '^'' '"^'^ ^^ould differ by be made by estimation IfZ tt '"'' '"^^"^^'^'^''"^^'^ temperature must two temperatures for which the inr'"'''"'"^'"^^ ^'^°"''^ ^'"^ between correction must be used d^ . " T''"°"^ ""'>' ^'■«"- °° '' ^''-t tab.e which is nearest!- ^e'tr^ t^^^^ ^^"^^^-^ ^ ^^'^ (07) Expansion or OilataHnn r, r , althoufjl, no, ,„,e unive " I v ,hn, 7 , °' ""= "'°^' P^^ *"". increases, it e^Jand T^ r "'"" ""= '""Pcratm-e of a body decreases; its drr:So::LdTcr,r. anTT^ '■"" "' '""''"""- t^crat^.^reu^so to i^s^Jrl;;;!:^;™ ^ "" '° '" ^°™" P u.-, »i{,n I + ) to a thermometer reading. INSTRUCTIONS TO OnSI'.RVKRS. 27 and shoulcf against the n the read- iperature is ases, is the n have the r, and the one being from the ed by the >.» ~r.2 °4 +2°0 '°.6 o°8 longer or oceeding rrec^ions differ by jre must between '°. I, that i in the rt true, a body lerature former se stated. ie stated, There is considerable difference in the expansion produced in different kinds of bodies by the same increase of temperature. The expansion is least for solids, it is greater for liquids, and greatest for clastic fluids, such as air. Thus ordinary glass acquires an increase of about .000015 of its volume when its temperature increases 1°, while for an increase of 1° mercury expands about .0001 of its bulk, alcohol about .0006, and ordinary atmospheric air .002. The expansion of water is irregular. As the temperature of water rises from 32° to 39°. 2, instead of expanding it contracts ; but above the latter tempefaturc it expands, although at an unequal rate. (68) On the Distribution of Heat among Bodies by Conduc- tion, Convection and Radiation. — Whether bodies be in close proximity with each other, or be separated by distances small or great, the heat existing in them has a tendency to distribute itself among them until they attain an equality of, temperature. This distribution of heat is effected by the following three modes : (i) By Co7tdHCiion. (2) By Convection. (3) By Radiation. (69) Conduction, and Conductivity or Conducting Power.— When the transmission of heat from one particle or body to another is effected by the successive heating of the intermediate particles by contact Communication, in the order reckoned from the warmer to the colder, the process is called "conduction." A familiar example is that of a metal rod held with one end in the fire, while the other is in the hand. When the particles contiguous to those in the fire receive heat from them, they in turn transmit it by contact to adjacent colder particles, and these latter to others, and so on, until after a time some of the heat reaches the hand. Substances differ greatly in the facility with which they conduct heat. If a spoon of metal be kept dipped in boiling water, the handle will soon become inconveniently hot ; while if the spoon be of wood or earthenware it may be held without inconvenience, because the wood and earthenware have not such a facility as metals for con- ducting heat. While the process by which heat is transmitted from particle to particle is called conduction, the substance in relation to that process is called a conductor, and the property whereby the body con- ducts heat with greater or less rapidity is its conductivity ox conducting power. ?8 INSTKUCTIOxWS TO onSERVEKS. J^^'J""' '^'■°"^'' ''^''^' ^'"' '^ transmitted rapWfy are said to be fatrtteT'r '; '^^^ '^5' -^^-^-^Z--.; Chereas those which The conductivity of metals is the greatest. Next in order to the a^r and otlier gases, and most liquids. The conductivity of mercury is much greater than that of either water or alcohol. ^ (70) Convection.-While it is by conduction that heat is transferred from parfcle to particle, the particles being at rest, the mode of tns ^rrcw-' '" ''' '''''' ''''''-' '''' ^^-«-^- ^--^--^ i' cir^ It is chiefly by ponvection, or tl,e transfer of heated particles from place to place, that heat is distributed through liquids and gases If heat be applied under a vessel containing water, the particles in the lower strata become heated, expand, become lighte; then the pa "ic les above them and are raised towards the surface by the act onTf t le cooler and heavier water. The cooler water, after its descen becom warm and ascends in like manner, until the whole mass is warm d may be seen that this process depends on the extent to which the liquid expands by heat, and also on the force of gravity and the consequent difference between the weight of the warmer and'colder portions oTthe _ Convection takes place in air and other gases more energetically than The diffusion of solar heat through the atmosphere is due in a great measure to convection. As the ground is warmed by the sun it for^ iXrThlnl'r.^^ ''' ''T ^°""" '-'' '^''^'-' ^^^^^ hghter than the cooler air immediately above it. is compelled to rise and o give place to that cooler air. The latter being warmed ascends !n iS turn and makes room for a further descent of cool air. and so on (71) Radiation and Radiant Feat.-When the passage of heat from one particle or body to another more or less distant is eff<.cted d^reafy, without the agency of intervening particles, the hea s std to • ra Zrhe t %: 'f^'^^^' ^^ '^^ '^^^ so transmitted is c^Hed radiant heat. The heat received by a person standing hefor. a fire is an example of radiant heat, for the heat does not relch'him by fir INSTRUCTIONS TO OBSKRVERS. 29 heating the intervening air, as may be shewn by the fact that the sensa- tion of heat ceases when a screen is interposed. The motion of radiant heat is so enormously rapid (probably the same as that of light), that the diffusion of heat by radiation would produce an almost instantaneous balance of temperature throughout nature, if it were not that heat leaves and enters bodies at a comparatively slow rate. The rate with which a body of a given temperature radiates heat is much the same as that with which it absorbs heat radiated from other bodies, and this depends much on the nature of the surface. Lamp- black radiates heat quickly, and the metals slowly. The rate with which a body cools by radiation throughout its mass, apart from the effect produced by other bodies, depends not only on the rate with which heat leaves the surface, but also on the rate with which its internal heat reaches the surface, i.e., on its internal conductivity, The actual rate at which a body cools depends on the amount by which its losses of heat by radiation exceed the gains obtained by absorbing the heat radiated from other bodies. (72) Specific Heat and Capacitor for Heat.— The quantity of heat which must be communicated to or abstracted from a given weight of a substance to produce a given change in its temperature, differs in different substances. Of two bodies of different material but of equal weight, that which requires more heat to effect a given change i its temperature is said to have a greater "specific heat," or a greater " capacity for heat." The heat necessary to add a certain temperature to water greatly exceeds that required for giving the same increase of temperature to an equal weight of iron or of mercury. Thus the heat by which the temperature of i lb. of iron is increased 1°, is only about o.ii of that necessary to add 1° to the temperature of I lb. of water ; or, as it is termed, the specific heat of iron as compared with water is about o.i i. The specific heat of mercury is 0,033 " " alcohol about 0.6 " " ice about 0.5 aqueous vapour about 0.5 A body which has a large specific heat requires a proportionately longer time to acquire the same change in its temperature than one of a small specific heat ; hence alcohol, whose specific heat or capacity for heat is nearly 20 times that of mercury, is vastly more slow than mercury in taking up the temperature of the surrounding medium. * r 30 INSTRUCTIONS TO OBSERVERS. SECTION II. ON SPIRIT THERMOMETERS AND SELF-REGISTERING THERMOM Spirit Thermometers. (78) Mercury becomes solid at -37°-9: when, therefore, a thermometei' is required for lower temperatures, it is necessary to employ alcohol for its construction, as alcohol has not been known to become solid at any temperature, however low. Alcohol is not so well suited as mercury for the construction of thermometers, chiefly for the following reasons: First, its inferior sensibility, occasioned by its large specific heat and low conductivity ; secondly, on account of the inequality in its expansion ; and thirdly, fron; its volatility. (74) Tniierior Sensibility.— The sensibility of a spirit thermometer, »>.,the readiness with which it takes up the temperature of the surround- ing medium, is impaired by the large specific heat of alcohol, and its loiv conductivity, 1 he former of these causes would not be so detrimental to sensibility (see Art. 72), if it were possible to give to the spirit the same volume as that of a mercurial thermometer, as, in consequence of the lightness of siiirit as compared with mercury, the quantity of heat required to effect the same change of temperature would be nearly the same in each case. It is not, however, possible so to reduce the volume of the spirit ther- mometer, a.s the weight of the spirit if the tube were vertical, or its cohesion if the tube were horizontal, would be insufficient to overcome the adhesion of the spirit to the glass, and the continuity of the column would be frequently broken. Moreover, a spirit thermometer is slow in taking up the temperature of the surrounding medium (air or water, &c.), on account of the very inferior conductivity of spirit as compared with mercury; in fact, the con- duction of heat in alcohol, as in other liquids (except mercury), is so slow that it is likely that the distribution of heat through the spirit is effected more by convection (Art. 70) than by conduction, and by the radiation inwards from the interior of the glass. (75) Unequal Expansion of Alcohol. -The inequality at different parts of the scale in the expansion and contraction of spirit which accompany changes of temperature, increases the difficulty of adapting INSTRUCTlOiNS TO OItSERVP:RS. 31 the interior volumes of the tube between the degree marks to the true change of volume corresponding to a change of one degree. (76) Volatility of Alcohol.— A serious defect in spirit thermometers is that caused through the volatility of alcohol, by which portions are sometimes evaporated and condensed in the further end of the tube, thus causing the instrument to give readings too low, it may be, by several degrees. To guard against the error thus produced, the readings should be frequently compared with those of a good mercurial thermometer ; and if it is found that the spirit thermometer gives too low a reading, its tube should be carefully examined, in order that any portions of spirit, or " blebs" as they are called, that have been detached from the main body, may be re-united to it. To do this the thermometer may be swung about its upper end, bulb down, or jerked in the direction of its length, so as to break the adhesion of the spirit to the glass. (77) Incidental Advantage of the large Expansion of Alcohol. — The large capacity which it is found necessary to give to the bore of a spirit thermometer, relatively to that of the bulb, to avoid a break in the column would necessitate a considerable contraction between the degree marks, were it not that the expansion of alcohol is more than five times that of mercury. (78) Self-Registering Maximum Thermometer.- The object of this instrument is to give the highest temperature that has occurred within any given interval of time. It is not capable, however, of giving the time when the highest temperature occurred. There are various kinds of maximum thermometers, but the instrument with which we are here concerned is that devised by Negrette & Zambra. In this instrument, which is a mercurial thermometer, the bore of the tube near the bulb is contracted or obstructed by the insertion of a piece of porcelain, such that, although the expansion of the mercury occasioned by a rise of temperature is sufiRcient to force the mercury upwards beyond the obstruction, the cohesion of the mercury is not sufficient to draw it back again when, in consequence of a fall of temperature, it contracts. When the mercury forms an unbroken column the instrument is said to be set. If the temperature remains constant, or if it rises, the column will continue unbroken ; but if the temperature falls, the mercury below the obstacle, as it contracts, will retreat into the bulb, leaving stationary 32 INSTRUCTIONS TO 01iSi:R\EkS. 1 I the column above. The readint,' of the upper extremity of the column will then be the maximum temperature that has occurred durinj^ the interval which commenced with the time of setting and ended with the time of reading. To set the instrument, which should be done as soon as it has been read, it is to be held by the upper end with the bulb down, and swung gently, or jerked in the direction of its length, till the continuity of the column has been restored. Care must be taken to raise the temperature of the thermometer as little as possible by the heat of the hand, as the thermometer will continue to indicate the temperature thus acquired, until its temperature has been exceeded by the increasing temperature of the air. If the temperature of the air should not attain to the tem- perature thus artificially given, the instrument will obviously give a false maximum which is higher than the true one. The maximum thermometer should be suspended in a nearly horizontal position, but with the bulb end slightly depressed to prevent the mercury from sliding towards the further end of the tube, which might happen if that end were lower than the contracted part of the tube. (79) Self-Registering Minimum Thermometer— A minimum thermometer is designed to shew the lowest temperature th .l has occurred within a given interval of time. The minimum thermometer commonly used is a spirit thermometer, containing in the tube a small index, which consists of two minute spheres connected by a fine short stem, and which slides within the body of the spirit, by which it should be always perfectly enveloped. The thermometer is suspended in a horizontal position. When the column is unbroken, and the end of the index furthest from the bulb (and which may be called the upper end of the index) coincides with the end of the column of spirit, the index is said to be set. If the temperature becomes lower the column contracts and draws the index with it, the upper end of the index still coinciding with the end of the column. If the temperature afterwards becomes higher, the index will remain stationary, and the spirit will expand beyond it. The upper end of the index will then shew the lowest temperature that . as occurred since the index was set. To set the index, the bulb should be raised and the index allowed to slide to the upper end of the column, the motion being aided, if neces- sary, by gently tapping the tube. INSTRUCTIONS TO OBSERVERS. 33 The errors to which a minimum, in common with other spirit ther- mometers, is subject from the evaporation of the spirit, must be provided against as explained in Art. 76 ; but before jerlcing down the detached portions of spirit, the index must be suffered to slide down to the bulb. It will assist the re-union of the spirit, if the thermometer be afterwards suffered to remain for a few hours suspended in a vertical position, bulb downwards. SECTION III. ON THE DETERMINATION OF THE TEMPERATURE OF THE AIR AND THE. MODE OF EXPOSING AND READING THERMOMETERS. (80) Temperature of the Air Defined— By the temperature of the air at a station at any time, is to be understood the temperature of such air as may be taken as a fair average sample, as repeats temperature, of the air in the neighbourhood at that time, within a few feet above the ground. It is a matter of primary importance that the air near the thermometers be not stagnant; as such stagnant air is likely to have the temperature which the air in the neighbourhood had at some previous time, and not the temperature at the actual time of observation. It is desirable therefore that thermometers be suspended at a distance from any building, so as to be freely exposed to every wind. (81) Thermometer Screen.— Supposing the thermometers to be placed in the air whose temperature it is desired to know, it is further necessary that they be so exposed as to take up the temperature of the air by contact with that air, while they are guarded from being heated or cooled by interchange of heat through radiation with the ground and other surrounding objects (which are liable to be warmer or colder than the air), or by parting with heat by radiation to the sky. This is effected to a great extent, although not perfectly, by suspend- ing the thermometers in a screen, which is a rectangular case formed on its four sides and bottom by thin louvre slats of sheet iron, which intercept heat rays, but freely admit air. The top is close, to guard against drifting snow which might possibly settle on it, and drop on the thermometers as it melts. The thermometers are attached to a frame formed of two strips of hoop iron stretched from end to end between the front and back of the screen. The ordinary mercurial thermometers are fastened to brass bows, the ends of which project forward, while the middle of the bows ^re screwed to the horizontal frame. The self-registering thermometers § M 34 IN.STRIM TIONS lO OHSKRVEKS. are susj.etuicd ]i(.riz,„itally by hooks, which by pinching screws can be so fixed as to {,rive the requisite level. (82) Thermometer Shed and its Supports.-As the screen alone IS insufficient to protect the thermometers from sun and rain, it is placed under a thermometer shed, which has a double roof, with an air space open to tlie cast and west, with sides of wooden louvre slats, with louvre doors on the nurtli face, and a back of close half-inch boarding towards the south. Within the shed and to the north side of its back, the screen is attached by four iron holdfasts, with an interval of two inches between the back of the shed and the southern slats of the screen. To protect the thermometer shed from the southern sun, it is attached at a distance of two inches to a double fence as represented in Photo- graphs, figures 2 and 3 at the end of the book. Figure 2 gives a view of the shed with its doors closed as seen from the North-West. Figure 3 gives a view of the interior of the screen as seen from the North. The screen, shed and fence are painted white. The dimensions in inches are as follows : Screen. Shed. Length from east to west 24 37 Depth from north to soutli g ,g Height ,g from 29 back 3 1 Double fence : Length from east to west 72 Interval between front and back 4 Height !.!."!!!!.! 84 (83) Locality of Thermometer Shed.— The shed, if possible, should be in an open space, away from all buildings, walls, fences, &c., which might interfere with the free circulation of the air, or by which stores of heat could be accumulated, from whence the thermometer sheds, &c., might be unduly affected by radiation. Wall Exposure. — When the premises are so circumstanced as to preclude such a position as that just described, the outer shed must be attached to the north side of some building, in a position that is not exposed to draughts from doors or windows, and where no high building IKSTRUCTIONS TO OBSLRVERS. 35 Stands within 20 feet from the thermometers, and to the north of the line of wall to which the shed is attached. When the shed is thus placed, the iron holdfasts of the shed, instead of being screwed directly to the wall, should be screwed to a partition formed of upright inch boards, which are nailed to and blocked out by two pieces of 4 x 4 scantling, fastened horizontally to tlie wall. The object of this partition is to guard the shed from radiation from the wall, which may be much hotter or colder than the air whose temperature it is desired to know. The partition should therefore extend at least one foot above, below, and beyond the sides of the shed. Window Exposures to be Avoided if Possible. -The practice of exposing thermometers where they can be read through a window is to be avoided if possible ; but if the premises be not adapted for other modes of exposure, .so that the choice lies between observations through a window and no observations at all, the shed may be attached to two scantlings stretched across the window,* with a sliding door fitted to the back of the shed, the screen being turned round so that its doors may face the south. It would be well also to fit a sliding pane to the window, which should be kept open as short a time as possible, when the self- registering thermometers are set. (84) Snow to be removed from the Screen, &c.— More snow must not be allowed to accumulate near the thermometer shed than is found elsewhere in the immediate neighbourhood ; and if snow has dis- appeared generally from the ground near at hand, snow and ice close to the shed should be removed. Snow that settles on the slats of the shed or screen should be kept brushed away ; and if snow settles on the thermometers, it should be carefully removed some time before an observation is taken. (85) No Rubbish allowed in or about Thermometer Sheds.— The thermometers, as well as the screen and shed, &c., should be kept tree from dust, cobwebs and rubbish of any kind, not only to avoid slovenliness, but because their presence impedes the free introduction and circulation of the air from outside. This objection is applicable to any articles xvhatever placed in the screen between the partitions, such as rain-glasses, note books, and even spare thermometers, unless suspended for use. * The windows must of course face nortli, or nearly so. 36 INSTRUCTIONS TO OBSERVERS. (86) To Read a Thermometer. -The better kind of thermometers are graduated on the s/em,and have also numbers indicating some of the degrees etched on the stem. Most thermometers have al.o an attached scale on wh.ch every degree is marked, and every tenth degree numbered- As the chief use of the attached scale is to aid the eye in reading the scale on the tube, if any slight discrepancy be not cd between the marks on the tube and those on the attached scale, it is by the scale on the (ude that the observer must be guided. In reading a thermometer, it is necessary that the eye be placed on a line from the end of the column of liquid perpendicular to the column* If the column be in an upright position, this line will be horizontal and the eye will be in the same level with the top of the column. Inattention to this precaution may cause an error of 2° or mc"e. The observer should avoid touchingf the thermometer before reading It. -r breathing on it, or warming it by a too close approach o*" the person • and at night he should not allow the ligh^ from the reading lamp to fall on the bulb, or on more of the stem than is necessary. SECTION IV. ON THE REGISTRATION OF TEMl-ERATURE OBSERVATIONS. (87) Hours of Observation.~At stations which are primarily /?«/« Stattons, but at which certai. observations of temperature are also taken the temperature observations consist either of readings of the ordinarv^ thermometer made twice daily, or of readings once daily of the self- registering maximum and minimum thermometers. For the ordinary thermometers the readings are 9 a.m. andopm while the self-registering thermometers are both to be read and set at 9 pm. (88) Rules for filling up the Columns of the Register.-The actual reading of each thermometer, withrut modification or correction shouxd always be entered in the Register, as the risk of error is thereby much diminished.^ ' „f^h^.'K^'"TruT- "°' "'''"'^' for a degree mark the reflection of that mark on the back of the tube. f he bnngs the mark, its reflected image, and the end of the column into apn^ent coaicidence. his eye will be correctly placed. apparent lonVLSr/!r™r""- ""^ ''T ^'"''^ ^^ "^""'"S ^»'" °' ^"°^' *' """^t be wiped sufficiently long before the observation to aUow it to recover its proper temperature register took. "«tniment, anu to transfer them horn the pocket-book to the INSTRUCTIONS TO OBSERVERS. 3; In the columns headed " observed " enter to tenths the actual readings of the thermometers, prefixing the sign (— ) if the reading be below zero. Under these readings write the index corrections, with their proper signs (+) or (— ), and apply them according to the rules explained in Art. 66, and enter the corrected readings in the columns headed " corrected." Examples : Observed. -4 Corrected. 34''.8 Observed, 32°4 +.2 Corrected. 32°. 6 Column " range." When a column for the range is provided, enter in it the difference between the corrected readings of the maximum and minimum thermometers. mmi^mm (|p||^|!RP!^pwi'^*srD^*'*'A,v