Connecticut western news., 1877-09-07
SCIENTIFIC.

Earthquake Waves.-At a recent meet ing of the California Academy of Sciences, the President, Professor George Davidson, of United States Coast Survey, exhibited an enlarged drawing of the regular tidal waves, and Of the recent earthquake waves that reached San Francisco Bay on the 10th of May, 1877, and supposed to have been occasioned by the terrible earthquake that destroyed the town of Iquique Peru on that day.
 At Fort Point the United States Coast Survey maintains self-registering tide gauge whereby a sheet of paper is drawn horizontally over rollers that are moved by clOckwork. The forward movement is nearly two feet in "A hours. Over this sheet of paper pencil moves athwartships. by the lowering or rising of the float box, and the wheel work is so prOportioned that one foot movement of the tide exhibits itself as movement of one inch of the pencil. The draw ing at the Academy was four times the length and breadth of the tidal sheet. On the sheet there is an apparent irregular ebbing of the tidal waters for a few minutes, and then 8 sudden rise, followed by depression, until six large waves, of about nine inches each, had exhibited themselves in the space of one hour and 20 minutes. The earth quake waves continued to nearly noon of May 18th, when the last one regis tered itself; but long before this it was evident. from the irregularity of time, elevation and form, that these were reflex waves reaching from far-off limits in the ocean. In fact, it seems likely that the reflex waves commenced certainly not later than the 30th, and possibly before that.
 "So far as we have been able to ascer- tain," says Professor Davidson, "the earthquake at Iquique occurred on the 10th of May, at o'clock, A. M., but we must await more definite information before endeavoring to decipher the readings of the tidal register. Assum- ing, however, that the earthquake occurred at l A. M., we know that the difference of longitude from San Fran cisco is 3 hours and 28 minutes, and that the first indication of the incoming wave occurred at hours and Is minutes at San Francisco. This would give 8 hours 46 minutes for the time occupied in the wave traversing 5,20O statute miles, mainly along the shores of South and North America, at rate of 600 miles per hour, 10 or miles per minute.
 tsThis is much greater than the pro- gress of the earthquake wave that left Simoda, Japan, on the 23d of December 1854, and reached San Francisco ill about l2 hours, travelling at the rate of 375 miles per hour, or 6'2 miles per minute. But the great waves of that earthquake were only eight inches in height and 35 minutes apart when they reached Jnf Tn fIa main principal waves were much higher, and their crests much further apart.
 Further information may place the locus of the earthquake away from lqulque. Upon this coast we ascertain that the earthquake wave was not noticed at open ports or landings, such as Santa Barbara, Gaviota, etc., but it's effects were exhibited in such 'harbors as Washington, Cayugas, and doubtless would have been especially noticed at the mouth of the Estero Limantour in Drake's Bay. In these harbors the rapidly advancing and rising wave would be concentrated as into 8 funnel and rise and fall rapidly and largely. It IS reported that the rise and fall was 7 feet at Wilmington, not noticed at Santa Barbara and Goviota. and 12 feet at Cayugas. The reported shock to two vessels near the entrance to San Fran cisco harbOr seems somewhat problem. atical. The waves entered the Golden Gate about l foot high and about 40 minutes long. We were at Fort Point at the time, and, with smooth sea, could detect no change of rise and fall on the beach, where very slight surf was running"
 News of the earthquake waves com ing in was telegraphed to Washington a hours after they commenced, and from their length and height it was predicted that great earthquake had occurred at distant place.