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 EARTHQUAKES IN CALIFORNIA, (1888). 
 
 By Edward S. Holden. 
 
 LIBRARY OF THE 
 
 USIVEESHI 01 CALIf OESIA. 
 
 LICK GBScRVATORY. 
 
[Feom the American Journal op Science, Vol. XXXVTI, Mat, 1 
 
 Art. XLI. — Earthquakes in California^ (1888) ; 
 Edward S. Holden. 
 
 In 1887 I compiled a list of earthquakes which had been 
 recorded in California, etc., from 1769 to the end of 1887. 
 This was printed by the Regents of the University of California 
 in a pamphlet of 78 pages and widely distributed. The data 
 there given have been discussed in two papers subsequently 
 written. The first is a note on Earthquake Intensity in San 
 Francisco (1808-1888) printed in this Journal for June, 1888 ; 
 aud the second has the title Earthquakes in California, Wash- 
 ington, and Oregon (1769-1888) and has been communicated 
 to the California Academy of Sciences. These three publica- 
 tions contain all the data which I have been able to collect, 
 and I believe that no deductions of especial value can be drawn 
 from the data except those which are there given. These 
 statistics could, of course, be tabulated in several different ways, 
 but it is my opinion, from trials, that no important results not 
 already given would follow. 
 
 The examination of past records has naturally led to the 
 consideration of the best manner of making future ones. The 
 object of such records is to bring to light all the general facts 
 as to distribution of earthquake shocks, as to topographic areas, 
 as to time, as to average intensity, etc., and also to enable a 
 study to be made of particular shocks, — as to velocity of transit, 
 area of the disturbed region, intensity, etc. In order to study 
 any of these questions with profit it is necessary to have some 
 kind of a measure of the intensity of each earthquake shock. 
 The most satisfactory instruments which I have seen for this 
 purpose are those invented by Professor Ewing, F. R. S. These 
 are devised on sound mechanical principles and are well con- 
 structed by the Cambridge Scientific Company. 
 
 It is necessary at the Lick Observatory to keep a register of 
 all earthquake shocks in order to be able to control the positions 
 of the astronomical instruments. Accordingly I ordered a set 
 of Professor Ewing's instruments for the Observatory, which 
 were delivered in 1887. They are described with woodcuts in 
 Volume 1 of the Publications of the Observatory, (page 81) 
 
E. S. Holden — Earthquakes in California. 393 
 
 and in the Hand Booh of the Observatory, (page 54). The 
 complete set of instruments will give for each shock the time 
 of its beginning, and that of every tremor ; the amplitude of 
 the vibration in the east and west, the north and south, the up 
 and down directions at every instant. Such a complete set of 
 instruments requires continual attention and is far too delicate 
 and troublesome in adjustment for general use. The Duplex 
 Seismometer of Professor Ewing seems, however, to be well 
 suited for general purposes. It gives with considerable accu- 
 racy, the magnitude of the earthquake force in any two 
 directions as east and west and north and south. The vertical 
 component is not registered, and the time of occurrence must 
 be taken from a watch. Copies of this instrument can be had 
 from the California Electrical Works (35 Market street, San 
 Francisco), for $15. It therefore seems to be a suitable pattern 
 for use in California, and elsewhere, since it combines compar- 
 ative accuracy, with cheapness. A complete set of Professor 
 E wing's instruments, is provided as I have said, at the Lick 
 Observatory. The duplex seismometers multiply four times ; 
 while the vertical component is multiplied ly^ times, the 
 horizontal component Z^-^ times in the complete instrument. 
 
 Another complete set, exactly similar, belongs to the Univer- 
 sity of California, at Berkeley, and is installed at the Student's 
 Observatory there, under cJbarge of Professor Soule. This 
 Observatory also has a Gray-Milne seismometer, complete. 
 Copies of the duplex seismometer are set up also at the 
 following stations : 
 
 (1.) San Francisco, near Cliff House, residence of Hon. A. 
 Sutro. 
 
 (2.) San Francisco, 917 Pine street, residence of Hon. J. R. 
 Jarboe. 
 
 (3.) Chabot Observatory, Oakland, in charge of Mr. Burck- 
 h alter. 
 
 (4.) Private Observatory of Mr. Blinn in East Oakland. 
 
 (5.) Kono Tayee, Clear Lake, residence of Capt. R. S. Floyd. 
 
 (6.) Observatory of University of the Pacific, San Jose, in 
 charge of Professor Higbie. 
 
 (7.) Students' Observatory, Berkeley, in charge of Professor 
 Soule. 
 
 (8.) One will be shortly installed at Smith Creek Hotel, at the 
 foot of Mt. Hamilton. 
 
 (9.) Office of State Weather Bureau, Carson, Nevada, in charge 
 of Charles Freund, Esq. 
 
 Copies of this instrument are also in possession of Warner 
 and Swasey of Cleveland, and of Capt. C. E. Dutton, of the 
 U. S. Geological Survey for experiments. I believe that one 
 will be shortly mounted at the Blue Hill Observatory, near 
 
394 E. S. Holden— Earthquakes in California, 
 
 Boston, Massachusetts. The Lick Observatory also possesses a 
 seismometer invented by Professor Milne and kindly presented 
 by him, which is designed to serve for general purposes. We 
 have not thoroughly tested this as yet. It is simple in construc- 
 tion, and inexpensive. A description of it may be found in 
 Trans. Seis. Soc. of Japan, vol. xii. 
 
 The instruments above named which are in California have 
 been visited and adjusted by Mr. Keeler of the Observatory 
 (who is in charge of our earthquake instruments), and the 
 owners of these instruments have kindly reported the occur- 
 rence of shocks, and have often sent blue prints or tracings of 
 the records made. The reports of Mr Jarboe, Mr. Blinn, and 
 Mr. Burckhalter have been especially full, as will be seen from 
 what follows. Wm. Irelan, Esq., Dr. J. B. Trembley of Oak- 
 land, and U. S. Surveyor General Irish of ]Mevada, have kindly 
 taken the pains to send accounts of all shocks. 
 
 I have also copied from such newspapers as fell under my eye 
 all data respecting California earthquakes. These are given 
 in what follows, together with the results obtained from the 
 various instruments. To make this record complete the reports 
 of the U. S. Light House Board, of the U. S. Geological 
 Survey, and the annual records of earthquakes given by 
 Professor Pockwood in this Journal should be consulted. As 
 these are available to all, I have not reprinted any data from 
 them. It is intended in future years to continue such records 
 as the present one. The extremely local character of some of 
 these shocks is noteworthy. 
 
 Earthquakes in California, 1888. 
 
 1888, January 7, 10:25 P. M.— S. F. (II) : Berkeley (lY),— 
 at Berkeley a loud explosion. — Professor Kellogg. 
 
 January 18, at night. — Berkeley, a slight shock (N.E.-S.W.) 
 recorded on duplex seismometer (I? II? III?). — Professor 
 Soule. 
 
 Jam^uary 16, 11:39 P. M. — S. F.: single, short, sharp shock 
 (lY). — E. S. H. (I have no other report of this, and it must 
 therefore be regarded as doubtful.) 
 
 January 17, 10:10 P. M.— S. F.~E. E. Barnard. Oakland, 
 from N.E. to S.W. (III? lY ?).— Prof essor Edwards. 
 
 January 26, ? — Healdsburg, 10 sec. duration, S. F. Chronicle, 
 Jan. 28. (Total eclipse of the moon on January 28.) 
 
 January 29, 10:35 P. M. — Carson, Nevada, a slight shock 
 (lY to Y) Grass Yalley, CaL: the same shock; (II). — Grass 
 Yalley Tidings, Feb 3. 
 
 Jam^uary 30, 4:15 A. m. — S. F. [not reported in newspapers]. 
 
 J. R. J. 
 
E. S* Holden — Earthquakes in California. 395 
 
 February 18, 2:50 a. m. — Fort Bragg : three severe shocks^ 
 (Y V) ; the first at 2:50, the other at intervals of one or two 
 minutes. Mendocino : three shocks ; the first at 2:55, the 
 others at intervals of three or four minutes. — (S. F. Bulletin^ 
 February 18.) 
 
 Eehniary ? about 4 A. M. — Menlo Park : sleepers waked (Y 
 or YI).~J. T. Doyle, Esq. 
 
 February 29, 2:51 p. m. — S. F.: on Montgomery street, peo- 
 ple alarmed (Y) ; Pine and Mason streets, more severe, (YI) ; 
 Washington and Mason streets, (YI). Two waves on duplex 
 seismometer (917 Pine street.). The motion of the earth was 
 
 «._K 68° W. to S. 68° E. l—^. 56° E. to K 66° W. 
 The shock h was most severe. 
 
 Berkeley : not felt, not registered. — Oakland : (II.) — Bel- 
 mont : not felt— San Eafael : (lY or Y) 2:48 p. m., E. to W.— 
 Santa Posa : 2:55 p. M., violent ; people ran out of houses, 
 (YI). — Petaluma : 2:55 p. m., walls cracked (YII) sound of an 
 explosion heard. The severest for many years.— Healdsburg : 
 2:44 p. M., light K to S. — Martinez : 2:45 P. M., two shocks one 
 minute apart (YI). — S. F. Alta^ Chronicle, Bulletin^ Feb. 
 29th and Mar. 1. 
 
 March 7, 7:54 A. M. — Pasadena : 7:58 A. M., (YI) ; from 
 N.W. to S.E., duration three seconds. — Los Angeles : a little 
 after 8 A. M. (YI)? "severest for 18 years; no damage to 
 buildings," no very heavy articles overturned (YI). [S^ote : 
 on 1883, Sept. 5th, a shock (YI) was felt at Los i\ngeles, 
 E. S. H.J — San Diego : scarcely felt (11). (Pasadena Daily 
 Star ; also S. F. Alta, Chronicle, Mar. 7, 8). 
 
 March 28, 1:41 A. M. — S. F.: slight shock, but sufficient to 
 awaken a sleeper (Y). Direction of shock nearly ]^. and S., 
 on duplex seismometer, 917 Pine street. Professor Davidson 
 says duration f second, and shock from W. to E. — S. F. 
 Bulletin, Mar. 29. 
 
 April 9, 7:50 A. M.— Kiverside : slight shock (lY) KE. and 
 S.W. (S. F. Bulletin, April 9, Chronicle, April 10.) 
 
 April 12, about 5:15 A. m. — Riverside : the shock sufficient 
 to waken sleepers (YI) with loud noises accompanying. Col- 
 ton, 5:30 A. M. (S. F. Chronicle, April 13.) 
 
 April 28, [8:45 P. M.] — On the Lick Observatory seismo- 
 graph an earthquake record was found April 29. From the 
 trace of this shock the following data are taken. The dimen- 
 sions given below are to be divided by 3*3 for the Horizontal 
 and by 1*6 for the Yertical components, to get the actual earth 
 movements. The times are given in seconds after a zero 
 epoch arbitrarily assumed. The pen which marks the W. and 
 E. components registered a line y*-^- of a millimeter wide 
 throughout. There appear to be widenings of this line as 
 
396 E. S. Holden — Earthquakes in California, 
 
 early as fifteen seconds before the zero second adopted, but 
 the amplitude of E. and W. tremors is never more than -^ 
 of a millimeter during the whole shock and the time of their 
 beginning cannot be fixed. I presume we have here a case 
 where the normal vibrations were strictly in an E. and W. 
 plane. The transverse vibrations which arrived later are there- 
 fore N. and S. and of their full size in the diagram. We may 
 then dismiss all further consideration of the E. and W. wave. 
 It had scarcely a measurable amplitude. At seconds the N. 
 and S. tremors begin to show ; the whole record of the vertical 
 component is lost till 17 seconds. 
 
 3 sec. th 
 
 e earth m 
 
 oved S. of t 
 
 he neutral 
 
 line V 
 
 5 
 
 
 N. 
 
 ({ 
 
 
 6 
 
 
 S. 
 
 « 
 
 
 9 
 
 
 S. 
 
 (( 
 
 
 10 
 
 
 N. 
 
 (( 
 
 
 Hi 
 
 
 S. 
 
 (( 
 
 
 13 
 
 
 N. 
 
 (C 
 
 
 15 
 
 
 S. 
 
 C( 
 
 4 
 
 16 
 
 
 N. 
 
 (C 
 
 
 18 
 
 
 S. 
 
 <( 
 
 j 
 
 V.) 
 
 
 N. 
 
 (C 
 
 * 
 
 and small tremors with a double amplitude of about \^^ (on 
 the trace) continue till ^^ seconds. 
 
 The vertical component as recorded by the machine is given 
 below : 
 
 At 18 sec. the earth moved above the neutral line l""™ 
 19 " below " i 
 
 21i " above " | 
 
 23 " below " 1 
 
 and tremors of not more than J""™ continue on the trace till 
 about 56 seconds. 
 
 We may assume for a basis of computation : 
 
 Number of waves in 10 seconds =4, 
 Period, about 2*5 seconds =:T, 
 Amplitude magnified, l""™, a=0-3"^™, 
 
 Velocity of projection =V=-7-^ = 0*75, 
 
 Intensity = — =1-90, 
 
 which corresponds to about I on the Eossi-Forel scale. The 
 period of these waves is very slow. 
 
 April 28, 8:48 p. m. — Reno (Nevada), a smart shock : three 
 waves in 3 sec, followed by a general trembling for 10 sec. 
 
E. jS, Holden — Earthquakes in California, 397 
 
 The time of tlie third and. severest shock was 8 h. 48 m. 38 s. 
 p. M. Direction S. to N. (letter from U. S. Surveyor General 
 Irish). Two other observers say W. to E. — Grass Valley : felt 
 in the Idaho mine below the 1600 ft. level, Alta, May 2d. 
 Yery heavy, lasting 5 sec, from E. to W. {Chronicle^ April 30). 
 — Grass Yalley : the Orleans mine was flooded. The shock 
 was at 8:45 p. M. and very heavy (YII). It was preceded by 
 a loud noise. The duration was about 5 sec, and the wave 
 was E. to W. Clocks stopped, plastering fell, and also tops of 
 chimneys. — IN'evada City : walls of courthouse cracked (YIII). 
 — At Marysville, Downieville, Truckee, Colfax and Sacramento 
 the shock was very strong (G. Y. Tidings^ April 30, May 2). — 
 Nevada City : two severe shocks at 8:48 P. M. preceded by a 
 deep rumbling sound. Direction N. — Dutch Flat ; 8:46 P. M., 
 severe from S. to N. People were badly frightened. — Stock- 
 ton : four shocks at 8:40, from K. to S. — Dixon, 8:45 P. M. — 
 Biggs : heavy shock " lasting 75 (?) seconds " [seven to ^nq, ? 
 E. S. H.], at 8:45 (YII) plastering cracked, etc. — Santa Eosa: 
 slight shock at 8:45, N. and S. (III).— Truckee : 8:47, duration 
 two seconds, (S. E. Examiner^ April 29). — Oroville : 8:45 P. M. 
 Short, quick shock. — S. F. : barely perceptible in third story 
 of 917 Pine street. No record on duplex seismometer in 
 basement (I). 
 
 April 30, about 4 a. m. — Grass Yalley : Tidings^ April 30. 
 —Downieville : 3:40 A. M. two light shocks (lY), (S. F. Bul- 
 letin^ April 30). 
 
 May 4, 1:55 P. M. — S. F., 917 Pine street, decided shock, 
 not registered on duplex seismometer, J. K. J. — S. F., slight 
 shock (II) of a few seconds duration, {Bulletin^ May 4). 
 
 May 6, 9 h. 42 m. 22 s. P. M. (E. S. H.).— Lick Observatory : 
 sadden shock (III) E. S. H., preceded by a rumbling noise 
 (PoRCHEE.) (Registered on duplex seismometer). 
 
 July 11, at night. — Susan ville: slight shock (lY??), S. F. 
 Bulletin.^ Jul.y IS- 
 
 August 14,* 9:57 a. m.— S. F., 917 Pine st. Intensity (II) on 
 P. F. scale. The duplex seismometer gives a looped trace on 
 the plate (magnified four times) 7°"" N.K.E. to S.S.W. (direc- 
 tion of first shock), 4™"" at right angles to this. The motion 
 of the earth was therefore S.S.W. to N.N.E. — Lick Observa- 
 tory : direction on the plate KK.E., of the earth S.S.W. The 
 trace is a wavy line (magnified four times) 8'°°' long. JST.^.E. 
 and S.S.W. with six waves 1™™ high at right angles to this. 
 Probably the shock was nearly vertical here. 
 
 September 10, 1:53 a. m.— S. F., 917 Pine street: slight shock 
 (II) not registered on duplex seismometer, J. R J. — Oakland: 
 slight shock, C. Burckhalter. Three shocks at 1:50 a. m. in 
 quick succession, attended by noise; windows did not rattle 
 
398 E. S. Rolden — Earthquakes in California, 
 
 (III?), Dr. Trembley. It waked sleepers in Oakland (V?), E. 
 Booth. — Berkeley ; slight. 
 
 September 15? — Lick Observatory: the seismograph started 
 at 6:15 A. m., but as the record was not like that of a shock, 
 Mr. Keeler (in charge of the instrument) supposes the tremor 
 which started the instrument to have been due to a high wind. 
 
 Septeniber 17, 3:51 A. M. — Lick Observatory : The seismo- 
 graph gives the following records (magnified 1'6 times for the 
 vertical, 3*3 times for the horizontal components). At 3 
 seconds after an assumed zero second, the vertical component 
 began its trace with a wave of period about 1^ seconds. The 
 amplitude (on the trace) is hard to estimate but is probably not 
 less than 6""" for the first semi- wave, then about 1"™ for a full 
 wave, and after this mere tremors until about 40 seconds. The 
 N. and S. component (magnified) was as follows: 
 
 At 4*3 seconds the earth moved S. of the neutral line 5™" 
 
 5-7 " 
 
 5-9 " 
 
 6-1 « 
 
 6*4 " 
 
 6-9 " 
 
 7-6 " 
 
 8-9 « 
 
 and tremors occasionally as large as J™"" continued until about 
 40 seconds. 
 
 The E. and W. component (magnified) was as follows : 
 At 4*3 seconds there was strong movement of the earth west 
 of about 3"™°' ; this was followed by a wave of period about 1 
 second double amplitude 2™™ ; and this again by another of 
 period J second double amplitude l""". After this tremors 
 continue for about 30 seconds. 
 
 The strata of which Mt. Hamilton is composed lie at a high 
 angle to the horizon and the direction of the stratification is 
 nearer N. and S. than E. and W. The earthquake instruments 
 are at the very summit of the mountain. This may account 
 for the fact that (at least for the shocks so far observed) the 
 vertical component is relatively large, and that the N. and S. 
 component (in the general direction of the stratification) is 
 usually far larger than the E. and W. component. The record 
 of this shock on the duplex seismometer is very interesting, 
 but it gives no information additional to the above. 
 
 'We may then assume as a basis of computation for this 
 shock : 
 
 Number of waves in 10 seconds =6 or 7, say 6|. 
 Period, T, of the representative wave =0*5 sec. 
 Amplitude of the representative wave (magnified) =2-5™™ 
 a = O-S"^™. 
 
 N. 
 
 u 
 
 2 
 
 on to 
 
 u 
 
 
 
 N. 
 
 u 
 
 2i 
 
 S. 
 
 (( 
 
 H 
 
 N. 
 
 (( 
 
 1 
 
 S. 
 
 (( 
 
 li 
 
 IsT. 
 
 (( 
 
 . 14 
 
E. 8. Holden — Earthquakes in California. 399 
 
 Velocity of projection =^^7|^=10'0. 
 
 Intensity = — = 126. 
 
 This corresponds approximately to Y-YI on the Rossi-Forel 
 jcale, according to the table in this Journal, June, 1888, p. 429, 
 ivhich was derived from Japanese shocks. 
 
 Chabot Observatory : the time of the shock is 8 h. 50 m. 
 dIus or minus one-quarter of a minute (W. Irelan, Esq.). It is 
 registered on the duplex seismometer plate as follows. The 
 first motion (of the pen, magnified four times) is 2°"°^ to the W., 
 then follow several small tremors towards the S.E. The mo- 
 tion of the earth is of course in the reverse directions. — Lick 
 Observatory, 3:51 A. M. : severe shock, lasting several seconds. 
 Strong vertical component (YI to Yll) observed by E. S. H. 
 Also on L. O. seismometer. — ^Gilroy, sharp shock : Santa Cruz, 
 heavy, (S. F. Call, Sept. 18).— S. R, 917 Pine street: very 
 slight, no record on seismometer, J. R. J. 
 
 September 23, about 11:30 A. M. — S. F., 917 Pine street : 
 very slight shock, J. R. J. 
 
 Octoler 3, 12:52 P. M.— San Miguel, S. L. O. Co.: light 
 shock, 2 sec. duration, N. to S. (III). Another at same place 
 at 1:02 P. M., quite severe, IS", to S., 4 sec. duration, no damage 
 done (YI ?), S. F. Chronicle, Oct. 4. 
 
 October 4, P. m. — Paso Robles : slight shock. — S. F. Report, 
 October 5. 
 
 October 4, 11 P. M. — San Diego. — S. F. Bulletin, October 5. 
 
 October 5, 4h. 41m. 30s. ± 10s. A. M — Chabot Observatory: 
 the shock was sufficient to waken a sound sleeper (YI). On 
 the duplex seismometer plate the trace begins with a tremu- 
 lous motion toward the W., followed by two sharp jerks to the 
 S. The motion of the earth is contrary to the motion of the 
 plate. 
 
 October 23 ? — Lick Observatory : During Mr. Keeler's ab- 
 sence the earthquake instruments were in charge of Mr. Hill. 
 On October 23, at 6 P. M., I noticed that the earthquake instru- 
 ments were in their usual state. I also noted at 9 P. M., October 
 24, that a shock had occurred previously. The clock dial of 
 the earthquake clock is divided to 12 hours (instead of to 24 
 hours as it should have been), and there is an ambiguity of 12 
 hours in the time of the shock, which is either 
 
 October 23, llh. 42m. p. M., or October 24, llh. 42m. A. M.— 
 The shock was sufficient to start the clock of the Ewing 
 seismograph, but the plate did not move. The duplex 
 seismometer plate shows a tremulous wave in the direction 
 N.E. and S.W. 
 
400 E. S. Holden — Earthquakes in California. 
 
 October 24, 2:50 a. m.— East Oakland : (Y) Mr. Blinn's 
 Observatory. The duplex seismometer plate shows a trace 
 from S. to N. in general direction. The first trace on the 
 plate is that of a single wave about 2m. in amplitude 
 (magnified four times) followed by small tremors. — Chabot 
 Observatory : the plate of the duplex seismometer shows the 
 first wave strongly towards the N.E. The trace of this wave 
 (magnified four times) is a straight line O"""" long. This is 
 followed by two waves of the earth as it regained its original 
 position. The motion of the earth is contrary to that of the 
 pen on the plate. 
 
 October 25, in the night. — Mr. Blinn's Observatory. The 
 duplex seismometer gives a tremor, and the general direction 
 of the trace on the plate is S.E. to N.W. 
 
 November 4, 3:36 A. M.— Lick Observatory (YI).— E. S. H. 
 Mr. Barnard gives the time as 3h. 37im., plus or minus -J m. 
 The duplex seismometer gives a very complex knot of curves 
 ending by a trace on the plate towards the S.W. The trace on 
 the Milne seismometer (in cellar of the Meridian Circle House) 
 cannot be interpreted, as the instrument had just been set up 
 and probably was not adjusted properly. 
 
 November 18, 2:28 P. M. — S. E., 917 Pine street : two shocks 
 north and south (YII) registered on seismometer. Another 
 light shock at 5:38 P. M. — J. E. J. — San Eafael : 2:30 p. M., 
 '^. and S.— Oakland : 2:29 P. M.; one chimney fell (YII?).— 
 Berkeley: 2:28 P. M.; duration 7 sec; a third shock at 5:35 
 P. M. (S. F. Examiner^ Nov. 19.) 
 
 Lick Observatory : not felt, not registered. — Chabot Obser- 
 vatory : 2h. 27m. 53s., very sharp shock ; 3:30, slight ; 5h. 
 37m. 20s., sharper than the second shock. The duration was 
 3 sec. The trace on the duplex seismometer is a very com- 
 plicated circular knot of 5 to 6""° diameter (magnified four 
 times) with a looped excursion of the pen toward the east 
 gram fi-Q^n the center of the knot, and another straight one 
 from the center to the W.S.W , also of 6™™. All three shocks 
 are on this single plate. — In Oakland no real damage was done. 
 Two or three chimneys were overthrown and panes of glass 
 were broken (YI, or YII ?).— East Oakland : 2:29 P. M., N. to 
 S., duration 2 sec; 3:45 p. M., very light ; 5:36 P. M., E. to W., 
 duration 2 sec — (S. E, Bulletin, ISTov. 19). — Napa : 2:36 P. M., 
 duration 10 sec. — S. F. Chronicle, Nov. 19. — Haywards, San 
 Leandro, Niles : not felt. — Mr. Burckhalter. — Clear Lake : not 
 felt.— Capt. K. S. Floyd. 
 
 It is also reported by Capt. Edmundson of the ship " Drum- 
 lanrig," that he found soundings of 35 fathoms, 35 miles S.W. 
 of the Farallones where no shoal is now known to exist. This 
 point will be determined by the proper authorities. It is 
 
E. S. Holden — Earthquakes in California. 401 
 
 supposed by some that the shock of N'ov. 18 may have pro- 
 duced this shoal which is not down on the charts. 
 
 East Oakland : Mr. Blinn's Observatory. The first shock 
 was severe (VI) lasting about two seconds. The time was very 
 approximately 2h. 27m. 57s. (Blinn). Mr. Irelan gives 2h. 
 27m. 54s. Trees and hedges were seen to move. A few light 
 articles were overthrown, pictures were displaced, a clock was 
 stopped, (its pendulum was in the plane N.E. and S.W.); 5 
 chimneys were thrown down on 23d avenue ; a noise was heard 
 after the first shock. The second shock was (II) at 3:48 P. M. 
 The duplex seismometer trace is a loop about l"""" in diameter. 
 The third shock was (III) at 5h. 38m. 45s. P. M. The trace on 
 the duplex seismometer begins in an ellipse 2°"" E. and W., 
 1™°^ ]^. and S., and then there is a confused record of tremb- 
 ling 3°^°^ :N".W. and S.E. by X^"^"^ at right angles to this. 
 
 Decemher 11, 3:29 P. M. — Lick Observatory : the shock was 
 sudden and (lY) in intensity. Time by watch 3h. 28m. 59s. ; 
 by earthquake clock 3h. 29Jm. — J. E. K. A humming noise 
 was heard after the shocks. There were two such at an 
 interval of 2 sec. The time of the last was 8h. 28m. 58s. plus 
 or minus 3 sec— E. E. B. Intensity (Y), time 3:28.8.— E. S. H. 
 
 The duplex seismometer gives a record (magnified) begin- 
 ning with a sharp straight trace to the N.W. 3°"™ long, then a 
 straight trace to the N.E. If ""^ long, then a straight trace to 
 the N.W. nearly 2"™ long, and at the end of this the pen 
 has recorded a confused tremor in a space about 1™™ square. 
 The record of the Ewing seismograph is as follows : (The 
 adjustment of the marking pen for seconds has been changed 
 so that there are 95 beats of the pen to I min. of time.) 
 
 There are very slight ^vertical tremors for the first three 
 beats ; they then vanish completely. Their period is from -J- 
 to ^ of a second of time ; their double amplitude is not above 
 -j^ of a millimeter. 
 
 The east and west vibrations last only for two beats though 
 the faintest perceptible tremor lasts until the twentieth beat 
 after the beginning. Their greatest double amplitude is not 
 above ^ a millimeter, and their period appears to be about -J a 
 second. 
 
 The north and south vibrations are well marked. From the 
 zero beat (beginning) until IJ beats there are marked tremors. 
 From IJ beats to 4f beats vibrations having a double amplitude 
 of about one- half a millimeter, and a period of about -J to J of 
 a second time. At the end of the 6th beat the marked tremors 
 cease and a very faint tremor continues to the end of the 20th 
 beat, and possibly to the end of the 33d beat. As a basis of 
 computation we may assume from the record of the north and 
 south component : 
 
402 E. S. Holden — Ea/rthquakes in California. 
 
 Double amplitude magnified 3-3 times =0*5"''^. 
 
 a— D'OS™"". 
 
 T =0-3 seconds. 
 
 v = -—-=\'1. 1= — =36. 
 
 T a 
 
 This corresponds to about II on the R.-F. scale according to 
 the paper frequently cited above. The intensity was, however, 
 lY or higher. 
 
THE UNIVERSITY LIBRARY 
 
 UNIVERSITY OF CALIFORNIA, SANTA CRUZ 
 
 SCIENCE LIBRARY 
 
 This book Is due on the last DATE stamped below. 
 
 AUG 1 5 1383 REC'D 
 
 MAY 2 8 1984 
 
 to? 1983 RECb 
 
 Series 2477 
 
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