May 20, 1887.] 



SCIEN'CJE. 



483 



— Prof. J. P. Mahaffy has in press a book on 

 pocial life in Greece. It includes a review of the 

 life and thought in all the Hellenistic kingdoms 

 from the time of Alexander to the Roman con- 

 quest. 



— The study of mathematical astronomy seems 

 to attract so few college students in this country, 

 that we have examined with some interest a 

 pamphlet just received, a thesis on ' Cometary 

 perturbations ' presented by Prof. W. Hoover for 

 the degree of Ph.D., University of Wooster, O. 

 About half jof the paaiphlet is devoted to a gen- 

 eral discourse on celestial mechanics, and the rest 

 to deducing certain well-known formulae for 

 cometary perturbations. ConsiderabJe work has 

 no doubt been done in the study of Watson's 

 'Astronomy,' but we should have been glad to 

 see the actual application of the formulae to some 

 of our recent cornels, following the example of 

 students of astronomy at the German universities. 



LETTERS TO TflE EDJTOE. 



*^*The attention of scientific men is called to the advantages 

 of the correspondence coluinns of SCIENCE /or placing promptly 

 on record brief 2}^Bli™'inary notices of their investigations. 

 Twenty copies of the number containing his communication 

 will he furnished free to any correspondent on request. 



The editor will he glad to piiblish any queries consonant with 

 the character of the journal. 



Correspondents are requested to be as brief as possible. The 

 writer'' a nam,e is in all cases required as proof of good faith. 



The Sonora earthquake. 



In this portion of the world, since the afternoon 

 of the 3d, have been occurring a series of seismic 

 phenomena, such as, so far as records or tradition 

 show, never have happened here. The telegraphic 

 (newspaper) reports possess the usual characteris- 

 tics, — gross exaggeration with utter iuaccviracy of 

 detail. I am securing data to aid in making a more 

 complete record of the phenomena, and make this 

 merely a preliminary note. 



The earthquake struck this town at 3.06 p.m. local 

 time, which, reduced to standard, gives 2.48. Prob- 

 ably the best description will be an account of 

 my own sensations. I had just noted the time, when 

 I heard a rumble such as made by heavy ore-teams 

 in passing. This noise increased ; and the building, 

 a two-story adobe, began to shake gently, then more 

 violently. By this time it seemed to me to be a 

 severe whirlwind, such as frequently occiirs here at 

 this season of the year. The shaking and the noise 

 increasing, I went to the front of the building, some 

 fifty feet, and looked out. Then it began to dawn 

 upon me that something of a serious nature was 

 taking place, judging from the looks of the crowd 

 on the streets. I then ran back to the place whence 

 I had started, picked up a child, and made vcij way 

 to the street. When the open air was reached, the 

 noise was like a continuous roll of heavy firing, Avith 

 occasional short peals like a sharp clap of thunder. 

 This ceasing, I looked at my watch, and found that 

 from the time I had noticed the first rumble until 

 the end, had been about 1.75 minutes. Allowing 



ten seconds for error, leaves 1.65. Of this time, the 

 duration of the severe shaking could not have been 

 over ten seconds ; the moderately severe, about 

 twenty ; and the trembling, the balance of the time. 

 Judging by the movement of some glasses and 

 statuettes on my desk, the general direction of the 

 shock was from south-west to north-east. 



The amount of damage done, so far as I can learn, 

 is trifling. No building of any stability has been 

 damaged at all ; neither has any one been injured 

 or killed. Persons riding or driving were unaware 

 that any thing was happening. In the Siilphur Spring 

 valley, about twenty-five miles east of here, some 

 fissures occurred in the bed of an old stream, and 

 water spurted out to a small but varying height and 

 in considerable quantity. These streams continued 

 flowing for two or three days, but at present all save 

 two are dry. These seem to be permanent, and are 

 running a small amount of water at ordinary tem- 

 perature. I have not seen them, and my account is 

 derived from the owner. I may mention as an amus- 

 ing fact, that, in less than an hour after they broke 

 out, they were taken up and located under the water- 

 laws of the United States. 



Succeeding the shocks, mountain fires were no- 

 ticed on many of the ranges. This gave rise to 

 the reports of volcanic action, which may safely 

 be set' down as pure imagination. No phenom- 

 enon resembling eruptive disturbance, so far as 

 I can now ascertain, has taken place in any part of 

 the section disturbed. 



At the time of the first and severe shock, owing to 

 the vibration and the rolling of bowlders down the 

 motmtain-sides, large clouds of dust arose : this, 

 with the noise, caused many who saw the phenom- 

 enon to think that the cause was eruptive. The 

 fires, with only two exceptions that I now know of, 

 were burning before the shock. Of these it is pos- 

 sible that they were not noticed prior to this, or, 

 what in my opinion is not improbable, falling 

 bowlders ignited the timber. This point I will try 

 to clear up. The San Pedro Eiver, a small stream 

 nine miles west of here, is reported to have a slight 

 increase of water. This is diminishing rapidly. 



The railroad-track of the Atchison, Topeka. and 

 Santa Fe road, at a point where it ran in an east and 

 west direction, was bent 4^ inches out of line, the 

 convexity looking south. The bend was about three 

 hundred feet in length. Succeeding the severe 

 shock during the following forty-eight hoxu-s, 

 marked and noticeable tremors occurred about every 

 half -hour. These were of greater or less severity, 

 but none approached the first. Had instruments 

 been here to record the motion, no doubt they would 

 have demonstrated a continual vibration. 



The heaviest shock, since the first, occvirred last 

 night about 9.30. One ludicrous incident was that 

 of an acquaintance, who, while driving along a 

 mountain-road, noticed large-sized bowlders begin 

 to start down the mountain towards him. He be- 

 came much excited, took his rifle, and alighted with 

 the intention of seeking vengeance on the perpe- 

 trators of the outrage. The falhng of some immense 

 bowlders weighing hundreds of tons just then, 

 changed his mind : he will not now hunt the author. 

 Men working at a depth of six hundred feet felt the 

 vibrations severely. Some said they became sick, 

 and all said that the bottom of the drifts or shaft 

 seemed to rise. Men working at one hundred and 

 fifty feet did not notice it so much. One crew of 



