V] <^ /a 7 ^3 ^3 %. ^ -^ ^e /a U/% IMAGE EVALUATION TEST TARGET (MT-3) 1.0 IIM IIIIIM I.I • 5 ■""= •^ IM 12.2 u 1.25 1.8 U 11.6 Photographic Sciences Corporation y m, V y co^ \'^' ^\ -v*^ ^ -% .V « .% 4^ %^ 6^ 23 WEST MAIN STREET WEBSTER, N.Y. 14580 (716) 872-4503 i? C/j CIHM/ICMH Microfiche Series. CIHM/fCMH Collection de microfiches. Canadian Institute for Historical Microreproductions / Institut canadien de microreproductions historiques O' 1Qft7 Technical and Bibliographic Notes/Notes techniques et bibliographiques The Institute has attampted to obtain the best original copy available for filming. Featu.' ^HiwirwWiWitNaBiuw . {From the Canadian Naturalist, Vol. VIII. No. (i.) TFIE EAKTHQUAKK OF NOVEMBER 4, 1877. (Uoiid lit the Novcmbfi- Moetiii.if uf tlio N'ntiiral History .Socioty, by I lUNCiPAL Dawson, LL.D., F.R.S) In the Cauadian Naturalist, Vol. V., first series, will be found uoteh on tlio eiirtluiuiiko of October 17, ISGo, with ;i summary of facts relating to the previous shock;- recorded in Canada, and some general remarks on their periods, local peculiarities and probable causes. The subject was continued in Vol. 1. of the new series, 'n connection with the earthquake of April, 18G4, and in Vol. v., new series, in connection with that of October 2()th, 1870. I may refer to tiiesi- notices for what is known on Canadian eartliquakes up to that time, and we may now con- tinue the narrative in connection with the somewhat wide-spread disturbances of the earth's crust in the present autumn. On January -Ith, 1871, a shock was experienced at Hawkes- bury, Ontario, but was not reported fru c any other place. A mon extensive earthquake occurred on May 22nd, 1871. It prevailed from the city of Quebec to the western part of Ontario. The time ibr Quebec is stated at ten minutes before two a. m., and tiiere was a seconu shock at twenty minutes past three. The time for Perth, Ontario, is stated at half-past one. It is noteworthy that this earthquake occurred at nearly the same time with that recently experienced. Since 1871 several minor shocks have been noticed from time to time, but did not attract much attention, and I have preserved no details in relation to them. That of the present mouth was probably the most considerable since 1871. It occurred at Montreal, at ten minutes before two on the morning of Sunday, November Uh. At Montreal there was only one distinct shock, preceded by the usual rumbhog noise, and sufficiently severe to be distinctly felt, and to shake window- .sashes and other loose objects, causing them to vibrate for several seconds. In so far as the published reports give information, the shock would seem to have been limited to the area along the river St. Lawrence, extending from near Tliree Rivers on the east, to Kingston on the west, and in a direction transverse to the St. Lawrence from Ottawa to the southern part of New England. In a paper prepared for the American Journal of l! Science, by Professor Rockwoo'i, of Princeton, ho dolinjs the aroa in question as that of " an irregular trapezium whoso angles are marked by Pembroke, Ont., Three Rivers, P.Q., Hartford, Conn., and Auburn, N. Y., and whicli is some 200 miles on its norchern and southern sides, about 300 miles on the eastern side, and 175 on the western." So far as can be learned from the reports, the shock seems to have beon most severely felt on the north side of the valley of the St. Lawrence and about Lake Champlain, or may be said to have had its oentro in the Adiron- dack and Green Mountain region. In the notice of Canadian earthquakes in 18(J0, I mentioned thit it had been observed that the greatest and most fre- quent shocks hive occurr^id i little aftor the middle and toward the close of each century. We are now approaching the latter period, so that possibly the last siiock may b(! the beginning of a series of similar phenomena. Since, however, there is no known reason for this periodicity, it may be a merely accidental coincidence, or may depend on some cycle of about half a century. If we add to the table of carthqutikcs in Eastern America, given in Vol. V. of the .V'ttur'th'sf, the more recent earthquakes observed in Canada, the proportion for the several months will stand as follows: — January, 9 earthquakes; February, 4 ; March, 5; April, 5; May, 7 ; June. 3 ; July, 4 ; August. ; September, 4 ; October, 8; November. 15; December, 8. Total, 7*^:. Thus of seventy-eight recorded Canadian and New England earthquakes, fifteen, or nearly one-fifth, occcured in November; forty, or more than half of the total number, in the third of the year, extending from October to January inclusive. Tlie pub- lished catalogues sliow that sinular ratios have been observed elsewhere, at least in the North'^rn hemisphere. Li .some earthquakes a low state of the barometer lias been observed, as if a diminution of atmospheric pressure was con- nected with the movements of the crust producing seismic vib- rations. This we can readily understand if a low state of the barometer should prevail over an area of the crust tending to rise, simultaneously with a high pressure over a sinking area. In this case a state of previous tension migln. terminate in a rent of the crust causinoj vibration. In the present ca«e no verv decided indication of such a cause appears, at least in so fir as this pari i "11. 8 I t ! I 1 of the Sf Lawrence valley is coucerned. Mr. McLeodiiiforms me that the mean barometer tor tlu^ week preceding the earth- quake was 29.7504, and for the following wook 30.0864. The barometer on the Friday before tlie earthqu;iko at 8 p. m. was 29.115, the lowest observed since Mareli hist ; but at 1.50 a. m- on Saturday it wa.s about 29. 907, which is very near the mean of November 1870, and also a little above the mean barometer of the place for the whole year ; and on Sunday afternoon it rose to 30.200. It would thus appear that the c irthquake was pre- ceded by a low state of the barometer, and (bllowed by one unusually liiuh for the season, and this rapid fluctuation was accompanied with much atniosplieric disturbance in the region of the Lakes and the St. Lawrence Valley. The weather map issued by the War Department at Washington for Sunday morning, November 4th. sliows ,i low barometer in the Gulf of St. liawrence and a high barometer in the Middle States — the area of the eartliquake being about half way between the ex- tremes. In connection with previous earthquakes it has been ob.served tlrit tlie greatest intensity of the shocks appeared near the junc- tion of tlie liaureiitian with the Silurian formations. This would be a natural consequence eitlusr of the propagation of vibrations upwards from deep underlying regions through the Laureutian rocks, or from the overlying sedimentary rocks to- wards these older rocks. In the case of the recent earthquake, this appears to have applied chiefly to the border of the Jjauren- tians extending round by the Ottawa and Kingston to the Adir- ondaeks, as if a wave propagated throuuli the Silurian formations had broken against the southern and I'astern sides of the Laureu- tian region, or a shock originating under the Laureutian of these regions had extended itself from then» into the Silurian rocks to the .>