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L'CTtamplaira filmA fut raproduit grica i la ginirositi da: Department of Rare Books and Special Collections, McGill University, Montreal. Laa imagaa suivantaa ont tti raproduitas avac la pius grand soin. compta tanu da la condition at da la nattat* da I'axamplaira film«, at an conformity avac laa conditions du contrat da flimaga. Original cop'aa in printad papar eovars ara filmad baginning with tha front covar and anding on tha last paga with a printad or llluatratad impras- sion, or tha back covar whan appropriata. All othar original copiaa ara filmad iiaginning on tha first paga with a printad or iilusiratad impraa- sion. &fid ending on tha laat paga with a printad or illustratad impraaaion. Tha laat racordad frama on sach microficho shall contain tha symbol — ^^ (moaning "CON- TINUED"), or tha symbol ▼ (maaning "END"), whichavar appliaa. Mapa, plataa. charts, ate. may ba filmad at diffar^nt raduction ratioa. 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Lorsqua la document ast trop grand pour itrm raproduit an un saul cliche. 11 est film^ i partir da I'angia sup^riaur gauche, da gaucha d droita. at da haut an baa, 9n pranant la nombra d'imagas nicassaira. Las diagram mas suivants illustrant !a m^thoda. rata lelure, a J 32X 1 2 3 4 5 6 (( « St. Lawrence Canals and Gradual Diminution of the Blscliarge of tlie River St. Lawrence. OF THE ST. LAWRENCE CANALS. There appeared lately in the newspapers a letter addressed to the Editor of the Montreal Herald, signed " J. B. Mills", in reference to the William.sburgh Canals, on the river St. Lawrence, of which it appears that complaints had Ijeen made, that the bottom levels are not laid suf- ficiently low, to afford a proper depth of water, and charging a blunder of engineering in "their construction. Mr. Mills in this letter says, <* as " the remarks imply a charge of blunder in engineering— and, as I *■• have acted a most prominent part in construction of said canals, it « is no doubt proper for me to notice said remark, .a the way of " reply, and I do so, not as replying to the exaggerations of newspaper " paragraphs; but in the face of the country, and in the view of the " relation which I have had the honor of holding to the Department " of Public Works of Canada, to state the circumstances and facts " which bear upon the subject of said remarks. But to the point—- *' what is this '^lunder ? " In substance it is said that the grades, or the levels of the botton* *' of those canals are not laid low enough with respeet to the St, Law- " rence." " I acknowledge that in the year 184<8, the water of the St. Law- *' rence — therefore, the water of these canals, has ueen lower, than. " would have been expected, from the information in my possession " at the time the levels were established, but I conclude that it is in " the future experience of the country to determine whether or not " an error has been made, to what ciFCumstance the error is justly " chargeable." By this Mr. Mills seems not to admit the country's experi- ence of 1848 — aUhough by him acknowledged that the levels of those ■■ I 2 canal3 are not sufficiently low, according to the low state of the St. Lawrence of that year, and of which he says, it was unexpected, — and demands upon whom this error is chargeable, or to what circnm- stafice. It certainly appears that the error of those levels not being sufficiently low for 184'8, in the present view can only be chargeable to the " information in possession at the time, the levels were esta- " blished,''^ for had this information been better, or probably a better use made of it, than apparently has been done, the Engineer would have placed those levels lower. Next he says, "the levels of those canals were established in *' spring, 1843. In determining the matter, the Engineer had in pos- " session the last available information of the variation of thsSt. Law- " rence during an intervr' of more than twenty years next preceding " 1843.— Query — Had ho not data of an interval long enough, to " determine the levels of these then proposed canals." " Can there be more than one answer to the question, and that the " interval is quite long enough. If so then the charge of « blunder- " ing' is unjust — as from the information referred to, the levels as esta- " Wished are right, with reference to the intentions of the Government." Here agp.ln Mr. Mills makes the "blunder" rest wholly upon the best available information and time of twenty years previous to 1843 ! but he does not state from what source, or upon what observation this informa- tion was, or how obtained ; — whether from a regular register of the levels for each of those twenty years, or only this collected from the or- dinary observations of those navigating the river, or from those residing that time on its banks. But admitting the first — would this register warrant the probability to have answered for establishing a canal lor the next twenty years at the minimum level of this time — even if such canal should be vianted no longer — and farther allowing this register had been extended to forty years, and not varying from the other, would a considerate and qualified Engineer think himself bound to establish his work on the minimum level of this period, while either period might be considered " sufficiently available information" in the hands of such Engineer. — Certainly not — an experienced Engineer from such information would have put his level below the minimum ti , a of Miose periods: fur it would not do to split hairs with the St. Law- rence. Mr. Mills does not inform U3 with regnrrl to the relation of his canal levels and the levels of these twenty years, that is, whether those levels were put higher or lower than the minimum level ! but he says " the levels of those canals as established are right with res- « pect to the waters of the St. Law-ence and the intentions of the *' Government, for this entire interval of time, which interval, tWepert- " dentil/ ought to be considered long enough, to indicate the levels that " should have been adopted.'' It would now appear that the "blunder" in establishing those canals is more chargeable to the St. Lawrence itself, which has done very wrong in becoming lower in I8t8 than in the preceding twenty years, (if this was the fact.) And still more, after the levels of those canals were established right by the Engineer, both according to it- self, and the Government intentions -espechWy as a presumed adequate time of twenty years, had been taken as sufficient, by which all its variations of level ought to have been shown, and moreover ought not to have been departed from thereafter. Ill 1834 the writer of this was employed by the Commissioners of th . then proposed Cornwall Canal, to inspect and report upon ita route as laid off by Messrs Wriglit and Mill?, in which Report it is stated regarding the levels to be made in establishing this navigation, ' I think it adviseable to construct all ihe locks to twelve feet water, * which would be a better proportional depth for this than ten feet as ' has been proposed for the Inland Canal — for although only ten feet « channel is first obtained on the river route, the additional two feet * may be progressively added as may be required, and the more easily * as a dredging machine, which I advii5ed, is now obtained for the « Lower Province, and is the most effective in use,'* and had this advice been adopted the bottom levels of the St. Lawrence Canals all through would have now been found two feet lower than those by Mr. Mills. Farther had the Cornwall Canal been constructed on the route laid • See printeU Report No. 7, of the Co»nmiMioners appointed to superintend ihe improvement of the Navigation of the St Lawrenee. 0"t by that Repurt-the navigation of this portion of the nver St Lawrence would have been much better adai,ted to steamboats than the present canal, and would not have cost much more than half the cxpence, which has been laid out upon it. Mr. Mills next makes the supposition of a forty years report show- >ng the river to have been much lower than in the last twenty years at the tm,e of establishing those canals, and that this Keport should be set asule, presumi.-g h was only derived from such and such shoal or rocks bemg bare ; although exhibiting a much lower level than his twenty years report j but which report cannot be depended on ; be- cause he says rocks and shoals are frequently moved and moveable by ice. It .s, however, very evident that had he established the canals at th.s lower level of forty years supposed report, a serious blunder mi^ht by h,3 own account nave been avoided. To {his he adds, « is the En- ^^ g.neer to throw awny said information, (of 20 years) in possession, ^^ and seek after this some level or other whereupon to establish his ^ levels ? I think not and for reasons-First, that that low level (of • 40 years) ,s absolutely unknown and cannot be ascertained ^ Secondly, whether low or not, there is no physical law governing the St. Lawrence, that determines that river will be so low again " As before, let it be admitted, that the lowest levels of the St. Law- i-ence had been correctly taken, for each of the twenty years, pre- ced.ng the establishing of the levels of those Canals b^ them or by the lowest or minimum level of that period. I would ask by vvhat c^nd.t,on or principle this river should not be found to varv from this in the next twenty years ? or to what limit and tin.e would those obser- vat.ons m this period warrant the extent of its future variations of level and how has it happened that it should make such an anomaly «n 18i8,and to have been so unexpected-or is it the fact that the state of the river in 1848 was one of g.-eat probability, from the very .nformat,on of twenty years preceding the time Mr. Mills had obtained b.s best information, (if such information was correct) and which state m,ght not be the least in opposition to its ordinary ruling causes^ It appears farther by Mr. Mills's opinion « there is no physical law governing the St. Lawrence that determines that river will be so low again." This, if true, accouiita for its unexpected low state in 18+8. The St. Lawrence then nuist have a free will of its own, by which alone it rises or falls, and consequently may choose any parti- cular year to fall unusually low, and who knows but fur the purpose of direct opposition to the Engineer's best information, and to the Ca- nadian government's intentions ! but I cannot see as Mr. Mills seems to see, that it may not be so low again by the same vvill, for this would presume upon some physical law governing that vvill hereafter, which had not been before in action, or that the Government with its Engi- neer had made a better and a mutual understanding for the future state of this river ! But rejecting this independent will of the St. Lawrence, let us inquire if there are any physical laws whatever which may act, or always have acted upon this river, and affect its rise or fall, and even account for its seeming anomaly in 1818. This enquiry at least may be somewhat interesting for the future, and even maybe useful information for the establishment of works upon it, in the hands of qualified and competent Engineers. 1 OF THE GRADUAL DIMINUTION OF THE DISCHARGE OF THE RIVER ST. LAWRENCE. If we turn our eyes upon a Map of the Contiri..it of North America, we see the Kiver St. Lawrence with its sources the Great Lakes, namely, Ontario, Erie, Huron, Michigan and Superior, and also that portion of land shown by the rivers and streams draining into them,— Now if we draw, or trace a boundary line around the heads of the streams, not lower than the confluence of the River Otta- wa with the St. Lawrence we shall find the surface within this boundary which is covered with water, or those Lakes, is at least equal if not greater than that which drains into them, a circumstance peculiar to the sources of the River St. Lawrence, and to no other known river on the Globe. Those lakes form great and collecting reservoirs, fror-i which alone the River St. Lawrence has its whole supply of water, and upon which the heaviest and most constant rains can only raise their surfaces, m r, very «mall degive, a-uj ihey bercne, a rog.lating power of the quantity of water issuing from Lake Ontario, or the diseharge by the St. Lawrence. Along with this we know that the average full of rain IS always very nearly e,,..al over the same county, or district, and con- Hoqnently the annual mean dilferences of ri.e or fall of those surfaces, will be confined within very narrow limits, or be almost insensible,' and also the annual mean discharges of die St. Lawrence be equally little varied, or be nearly constant, that is supposing anv diminishing causes suspended, or that these discharg.'s shall be the 'full cITect of the rains and drainages. This is one physical law governing the River St. Lawrence. Another oi>crating mfluence upon the sources of this river, is the evaporation over the same extent of surface, as that of the rains, and which we had supposed suspended in the above law, but which acts considerably in diminishing the rain supply, or that which would be g.ven without evaporation by the rains. In fact, the rains without evaporation would regulate the full supply at nearly an equal or a constant (,uantity annually, this evaporation would also regulate the supply, only it would be of a much less constant quantity. Also as the average temperature annually of the same parallel of latitude is found to be nearly equable, the diminished supply by evapora- tion, would be only alTected proportionally, and be annually less, or more, in a very small dpgree, and thereby leave the annual difference, or supply always nearly etjual, and consequently the discharge of the river of little or no annual difference. This is another and second physical law governng the St. Lawrence. Now seeing that there are two distinct and special operating powers or physical laws relative to the St. Lawrence, the one neutralizing to a certain and constant extent the other, and thereby limiting within moderate bounds the discharge of this river, whichgives it that peculiar character of being confined within the difference of two feet in its annual rise and fall, our next enquiry is, how the St. Lawrence may he subject to any anomaly from this difference, or that this would be- come very disproportionate in certain years to that of others, and which anomaly might lead us to suppose, that some foreign cause not usuallv nrting upon this river, had been produced to dirninish pxtraordinarily, or increase its supply. Sui-h, an is presumed, was the first that had taken place in 1848— contrary (if true) to previous twenty years observations of its levels, according to the engineers of the Canadian Board of Works. It has been stated above, that the average quantity of rain is annu- ally nearly equal, and also the same, of the annual mean emperature ; but the truth is, neither of these is ever exactly eqtial . aseach is somewhat greater or less in one year than another, and their annual dilTerences can only be ascertained by proper registers being kept of them for each year, in which their proper measures have been taken ; but we know'that if the rain average of one year be increased over another, ti»e mean temperature of same year will in all probability be diminished ; so in this case the differences in lesser evaporation would increase the sup- ply, to add to the increase of rain ; the supply always being the difference of their respective eff cts, or the diflerence of the supply of the supply- ing power, and the evaporative power. On the opposite, if the rain average of one year is diminished, the mean evaporative power will be increased, and consequently the supply of the Lakes would be dimin- ished ; for in dry seasons the mean temperature is usually higher. Hence we see as the variations of effect, of those two different powers which make supply, that this supply will at the same tinie be also variable, thereby producing variations of the lakes surfaces, in a lesser or greater degree above or below the mean height of the time observed, or period of annual observations. And thus were these va- riations equally alternating and periodically taking place, the hydraulic mean height of these variations of the lakes surface, would be in a plane similar to the invariable plane of the Heavens, made by the oscillations of the planetary orbits, and be for ever stationary, while this mean would give a discharge equal to the sum of the discharges of the varying heights of the same time, and consequently :he annual discharge, of that or of other periods of the St. Lawrence, would also be invaria- ble ; but without a proper register being kept of the rises and falls of the surface of Lake Ontario, and other elements ..f this physico-mathema- tical problem,it cannot be SKcertained directly at the present time.— That 8 is whether ihia mean height to any g.ven period .» constant, or return! periodioally, to be in the same invariable plane, or whether it is altering from this in only one direction in reln'.ion to a given height. How- ever, it is obvious from the above, that the supply is the efiect of theso two powers, or laws, from their opposite tendency, acting in the same time, and the variations of this can only oscillate within narrow limits, with some small and gradual alteration from such plane, which effect may be considered to be the .pecial physical law governing the discharge of the St. Lawrence issuing from Lake Ontario. To follow our inquiry in the absence of registered observations, wc shall noiv call in common observation of cause and effect within our daily and ordinary experience, which may lead us to conclude at least, upon some, or the mo.t probable results, to be expected from the operating powers now directly producing the supply of water on those lake:^,-also regarding its change or variations in quantity, from other or indirect physical influences to which these powers may become, or are now subject. We have seen the effect of the two powers is this supply arising from their opposite tendenc.y,-the one filling by the rains and the other di- minishing by evaporation, and it is evident tliat in the event of the evaporative power being the greatest, that the supply by the other would come to be successively reduced ; so as to afford no discharge, and ultimately render those lakes totally dry ;_0n the other hand were the supply by the rains greater than the evaporative power can raise, the result would be a discharge, and if both equal, any discharge ex- isting at the time of their becoming so, would be reduced to the bed of the "outlet, at which level the surface of the lake would afterwards remain stationary with no discharge; and in every case of discharge, the quantitv discharged, together with that raised by the evaporation over all the lakes, will always be e(iual to the whole or full supply made by therains in the same annual time: but if the supply wasonly increased, this would not alter the last equality, but would raise the altitude ofthe lakes surface, and consequently its mean hydraulic height,* always sup- • The mean hydraulic height is that which would uniformly give the discharge equal to the discharge made by variations of level in the same time. r t 9 posing iliero are no other wurces of supply than by the n.\m and druinagea. We believe it will be admitted that there has been no successive in- creasing ride of the lakes form'ng the supply of the St. Lawrence, or rather Lt.ke Ontario to which we may only now refer, as being the collecting reservoir from which the St. Lawrer.ce directly issues ; for a successive increasing rise of this lake, would at least indicate u succes- ■ive greater annual fall of rain, or a continued annual decrease of the mean temperature, which has yet not been observed ; as little have ocular marks upon itsshoresshown, that this istaking place, and we can- not in the present inquiry recog.iize any other cause that would make a permanent rising of this lake, and consequently we cannot suppose that its hydraulic mean height, has ever risen increasingly from a lower to a higher level ;~Hencc the discharge of the St. Lawrence could not have gradually been on the increase. Respecting the only possible states of this lake as stated above, that is, if the hydraulic mean height is permanent; or if this mean height is on an invariable plane of the lakes surface, or if this plane varies from a higher to a lower level, we have shown that the first can only be accurately known, by having a register of its heighc, for a series of years, which would sliow if its mean annual oscillations would re- gult in a constant nican height, or give this mean, at a varying lower level. In the absence of this register we can only refer to the proba- ble results which might arise fiom the laws we have already found established, and that govern the supply, combined wiih any known alterations these may be subject to, caused from local or other influences not yet introduced ; for regarding the latter state, or increasing depression ol the mean height, without such influences, there are the same opposite objections as for an increasing rise, which is, that this depression would indicate a successive de- creasing annual fall of rain, and increasing mean temperature, which I believe is yet equally hitherto unobserved as of the contrary, or that the evaporative power and discharge together, had become greater than the full supplying power by the rains. B -•^ 10 In the case of the latter state being supposed ihere consequently must be another, and additional source of supply to make this state possible.— Then let us first examine how any such additional supp'v would be derived, and be at the same time consistent with, or co-exist wiih the known causes of that by the rains. If we take an ocular survey of those lakes we shall certainly find many evident marks, showing that their waters have covered a greater extent of surface, and from which now they have receded, namely, marshes along their shores which have been formerly under water, and have every indication of having been the ancient bottom, the same also may be observed along the St. Lawrence, for which we have not need to refer to any general deluge; but only to the simple and ordinary operations of nature, which have left the same marks on the shores of every body of water detached from the Ocean, that is found both above and below its level— as those above the level of the ocean may have been brought to lower levels by a gradual deepening of their outlets b; the continued action, or attrition of their issuing cur- rents, although by slow or almost imperceptible degrees ; while others might be from very remote eruptive causes, which would bring the lakes' surface to a lower level, by making a wider or deeper opening in the outlet. The first, however, would cause no increase or decrease of the discharge, but the other would instantly increase this, by drawing off a portion of the ancient waters that were previously below the level of their former outlet, to the level of the new one so made, but which would be speedily exhausted, and the lake would be reduced to its first discharge.- Hence in both cases the equality would again be that of the discharge, together with the quantity raised by evaporation, to the full supply by the rains.— Again those lakes found below the level of the Ocean must have been so reduced in iheir levels, by the evaporative power becoming greater than the supply by the rains, which is allowed to be the effect on the Caspian and Dead Seas ; therefore from all the observations made upon the sources of the St. Lawrence which we have yet introduced, we can only come at the conclusion at the present time, that the discharge of this river is alone the production of the rains, and would remain with its mean height stationary, provided no other addi- f i* r 11 tional source should be found, or foreign cause, either to enlarge or lessen it. Let us examine if there may be any such. If we look again upon the Map of North America, we shall see that there are few rivers of any great magnitude, that fall into the Lakes Superior, Michigan, Huron, Erie and Ontario, and those that do, are short in their courses, and for the greater part through flat, at least not hilly country, and the whole drainage by them, would ap- pear to be small, and affording a very limited supply of water, compar- atively to the great collecling and evaporating surfaces, presented by those lakes ; for if we begin at Kingston and survey upward through- out the whole of Upper Canada, and thence along the northern shores of Lake Huron and Superior, the rain drainage of the whole of this looks very small, by its extending not far from the shores ; as that on the first, there is no river of '.ny magnitude or length of course as a feeder, which would add sensibly little to the volume of water, and great surfaces of those vast inland reservoirs. Also in returning around, upon their southern shores, the same drainage appears equally limited, for the drainage of the Mississipi, Illinois, Wabash, Miami, and Ohio Rivers draw all nearly off from the shores of Superior, Mi- chigan and Erie, and with some exception of that which drains from New York State into Lake Ontario by Genesee, with a few other rivers of no great extent. On the other side the tributaries of the Otta- wa, and those that empty into Hudson Bay, draw off their waters very near to Lakes Huron and Superior, thereby leaving only a narrow belt of land drainage, surrounding those great lakes, and fr. m which they can apparently have no other supply of water, but the rain which falls on their own surfaces. In taking the above view, it may appear that the drainage if measur- ed by the apparent magnitudes of the rivers discharging int., those lakes, U^gether with the lains on their surfaces, is much smaller than that discharged by the St. Lawrence j but as we have no correct means at the present time of ascertaining this, we can only add a conjecture of there being an additional supply to that by the rains.-There seems to be some probability of this supply having a real source as has been impressed upon the mind of the writer for some years past, by the fact. im^m 12 that by some measurements which have been made, Lake Superior is found to be six hundred and twentr-seven feet above the level of tha sea, and its bed tlu-ee hundred and thirty-six feet below that level, to- gether living a total depth of nine hundred and sixtythre. feet, thus forming an immense concavity in the country, which if connected with the ocean would instantly be filled to the depth of three hundred and thirty-six feet of salt water. Now let us suppose that th.s con- cavity was instantly emptied of its present contents, and all the streams issuing into it at the same time stopt above its present surface level ; here then we would have an im.r.ense empty concav.ty wuh its bottom much below the level of the Ocean, and much more below all the standing and living waters of the surrounding continent for hun- dreds of miles distant.- Also as this concavity may have been formed from a very remote eruptive cause, its geological structure will be m all probability, wholly declining or dipping towards its centre, through Which the filtration of water from a considerable distance may from all sides collect into it, and thus form a supply to this lake over and above that by the rains, and in all probability be an annual con- stant quantitr, to discha.-ge by the St. Lawrence, but would maintain the mean height of Lake Ontario at a higher level than by the latter onlv. However, the above supposed additional supply to the rams may be, or not be, we have not yet found any cause, which would progres- siv'ely raise the mean height of the lakes, or annually increase the sup- ply, and therefore our last enquiry is to find ifthei-e are any to succes- sively depress this height, or by which the supply may be annually lessened. In all countries covered with foi-ests, the first step of occupation is to clear them otf tor the cultivation of the land, which is generally done along the borders of the rivers, thus exposing the sui faces of both lar,d arid water on a g,-e ate r exte.it to the direct rays of the sun and to the sweeping winds ; which exposure consequently will greatly incease the evaporation over those surluces, many times more, than when under entire shade, especially to the latter ; also the cultivation of the land by turning up and opening of the soil, gives it an additional absorbent I if I Id power to hold the rain3 for vegetation and for exhalation, ^hlch before would run off upon a hard or saturated surface. It is therefore evident that the clearinsand cultivation of the country must .n a very great degree increase the evaporation, and consequently d.mmish or dry up the numerous small streams and rills which contributed to fill the larger channels and rivers, hence in the event of these changes be- ing extended over a great surface of country, the rivers of that country mu'^t have been al.o considerably diminished, and progressively as those clearing operations had advanced. If we now apply these etTects to the belt of land surface, draining into those great lakes, it is cerlam the supply of water will be diminished in proportion to the new cleared surface so exposed to greater evaporation, and consequently the dis- charges of the St. Lawrence lessened. Such din.inulion of this m.ght not be remarkable in one age,and therefore could not be almost ocularly ob- served by those most familiar with it, until made somewhat conspicuous by another coinciding cause, producing a like eirect,such as one or two successive dry seasons, by which the level might then become com- parable to some recollected mark, but without suspecting that the difference had been made chiefly progressively. From those dunm.sh- ing causes it is easy to account for the low state of the St. Lawrence in 1818. , , , At the comrr.encement of clearing off the forests, this work would proceed very slowlv : b-. as the population increased this would go on more rapidly, especially in a country continually supplied by adult population, as that draining into the Lakes has been ; and conse- quently the diminution of the St. Lawrence from an increased evapora- tion within a few years back must have greatly increased, more than m the same previous period, as any diminution from this cause must have only commenced after the first settlement upon it, which may not ex- ceed fifty or sixty years back and for some time this diminution would be insensible. The above evident causes of diminution may have been added to, by the average fall of rain also diminishing, from the same clearing of the forests; for it is allowed that rain is the production of changes of temperature of the atmosphere, or from the conterminous sur- 1 11 faces of motat volurhes of the atmospnere of different temperatures intermingling, by which a portion of that moisture i« deposited in the form of rain ; then such volumes of different temperatures are much more likely to be produced from standing forests and wooded swamps, than from a country entirely open and affording a free circulation of temperature in its atmosphere,-lience the annual average of rainmay be also decreased. As stated above, a country covered with forest,-as a great por- tion of North America is, the clearing of this is the first and absolutely necessary operation in agriculture, and the only general improvement for a long time to come, atlea^t until the dry lands ate cleared and used for cultivation, and leaving the moist and marshy land untouched for direct farming purposes.-Again when the first are occupied by a dense population, draining the other will follow as the next improve- ment, this being in all countries only practised when the dry land be- comes scarce, and much increased in value, or in very moist climates in which it is required on the dry lands to prevent them from being chilled by overmoisture._Also whenever draining becomes a general practice and use in a country, it is obvious that it will be most effective in accelerating the surface waters to the main streams and rivers, and often so rapidily during heavy and continued rains, as to cause some- times calamitous inundations in their courses.-Consequently a gen- eral system ot agricultnral draining, around those great lakes, would be a considerable means of adding to the supply of water, vvhich first would certainly be much di.ninished, by the increased evaporation caused by the first clearing of the land. But such a system cannot be expected to be in operation to have such general effect for ages yet to come, while the clearing of the forest on the shores of T.akes Ontario, Erie and Huron will proceed every year with a geometrically progressive pace.— Hence every succeeding year will the evaporative power be many times increased over those clearances, and the supply to the lakes diminished, which is now become very visible in 1848, and which will continue as a certain result of the opposite tendency of the rains and evaporation over this portion of country. So far in the above, I have endeavoured to expose the natural «» •*■ «• 15 causes which both produce and regulate the uischargea of the River St. Lawrence, and this in the absence of any registered observations of them-or even of the annual variations of this river-which ,f I were possessed of, might have led to sonae determinate values or quan- tities as elements for the solution of this physicc mathematical problem. It is fortunate as it is, that we sometimes are enabled from our daily and ordinary observation and experience, to trace the operations of many of the laws of nature, and follow them in their apparently mys- terious courses-and if we cannot exactly measure or definitively mark theh progress in each step-yet, we often may at least detect as it were nature in her positive tendency or directions-and thence draw conclusions as to her most probable or predominating results. PETER FLEMING, Civil Enginter. DoKOEE» January 7, 1849. «V