392 



8CIEJ^CE. 



[Vol. IX., No. 220 



states, particularly the sylva, with the intention of 

 illustrating a work on the indigenous trees of Cali- 

 fornia. He must have left a large and valuable 

 series of figures, if not a completed monograph, of 

 the botanical forms of the region referred to. 



The published results of his various and prolonged 

 investigations have appeared from time to time in 

 the Proceedings and bulletins of the California 

 academy and elsewhere ; and his name holds a con- 

 spicuous place in all of the principal works relating 

 to the botany of the western coast of North America. 



In 1867 he visited the then Russian territory of 

 Alaska in the capacity of surgeon and botanist to 

 the special expedition of that year, having received 

 the appointment from Prof. George Davidson, who 

 had charge of the scientific division on that occa- 

 sion. 



Of his personal qualities, all who knew Dr. Kel- 

 logg will bear testimony to his simplicity, genuine- 

 ness, and purity, and his invariable kindly disposi- 

 tion. His was altogether a rare and most lovable 

 character. It may properly be said that his nature 

 was in many ways as attractive as the beautiful forms 

 he studied. Considering the period of his arrival 

 in California, and the ruling passion and influences 

 which governed the community at that time, as com- 

 pared with his refined tastes and quiet ways of life, 

 a most extraordinary contrast is presented. In the 

 light of ordinary experience, it is hardly conceivable 

 of a human being, among human beings of the same 

 race, more absolutely out of place than he. How- 

 ever incongruous the surging tide and rush of 

 affairs about him, he held the noiseless tenor of his 

 way. His gentle life has passed. He will be affec- 

 tionately remembered by many. B. E. J. S. 



U. S. nat. mus., April 16. 



The barometer during thunder-storms. 



A sudden increased height of the barometric col- 

 umn lasting a short time, which almost invariably 

 occurs with thunder-storms, has recently attracted 

 considerable attention. German writers claim that 

 notices of the phenomenon can be traced back to 

 various observers in that country for more than one 

 hundred years. Dr. Hellman finds a notice of it in 

 the work of Herr J. J. Planer in the last century, 

 and Dr. Ferrari finds a notice of it in the writings of 

 Toaldo of Italy in 1794. 



Mr. M. J. Johnson spoke of it in a paper read be- 

 fore the British association for the advancement of 

 science in 1855. Since the somewhat general intro- 

 duction of barographs, it has been so frequently and 

 so widely noted, that I think it is now accepted as a 

 characteristic ijhenomenon of thunder-storms. 



Dr. Cirro Ferrari, however, claims that the little 

 ridge of increased pressure attending the thunder- 

 storm is only a part of the phenomenon. In front of 

 this ridge he claims that there is a small trough or 

 area of diminished pressure, and the most violent 

 part of the thunder-storm falls between the two. 



There are, however, a number of well-authenticat- 

 ed cases in which the barometer showed no indica- 

 tions of a diminished pressure preceding the passage 

 of the storm, but showed an increased pressure dur- 

 ing its passage. One of the most marked cases is 

 given in the American meteorological journal (vol. i. 

 p. 156), where it is shown that during the passage of 

 a thunder-storm the barograph at Ann Arbor, Mich., 

 rose .13 of an inch ; but for ten hours preceding. 



and for twelve hoiirs following, the storm, the re- 

 corded pressure did not vary perceptibly from 28.94 

 inches. 



No marked thunder-storra has passed over Blue 

 Hill since the starting of the barograph at the ob- 

 servatory, without giving indications of an increased 

 pressure during the storm ; but only a few have 

 given indications of a diminished pressure preceding 

 the storm, except the slow, steady fall of pressure in 

 a general storm, or broad secondary, within which 

 the thunder-storm occurred. There have, however, 

 been a few marked cases of a decided diminution of 

 pressure attending certain storms. So far as the 

 records show, all of these storms M^ere attended by 

 very high winds. In a few of the cases the 

 sharp depression of the barometer lasted fifteen or 

 twenty minutes, and was followed by a rise lasting 

 slightly longer. One of the most marked cases oc- 

 curred on July 21 , 1886, and the depression lasted only 

 a few minutes. A copy of the barograph trace dur- 

 ing this storm is given in the following diagram. 



29.1 



29.0 



This thunder-storm, which Avas characterized by 

 very vivid lightning, lasted from about 5 to 5.45 

 P.M. It was attended by a most violent squall, 

 lasting from 5.12 to 5.17 p.m., during which a large 

 dog-kennel was taken up and smashed to pieces, 

 rain-gauges were overturned, and other damage 

 done. During this squall the barograph pencil fell 

 about .10 of an inch, giving the trace as seen on the 

 diagram. Overlooking this sudden fall, it is seen 

 that there was a gentle upward swell of the baro- 

 graph curve, lasting thirty or forty minutes, during 

 the passage of the thunder-storm. 



I am led to infer that the sudden fall of pressure 

 was due to the dynamic effect of the wind in sucking 

 the air out of the building, while the rise in pressure 

 was due to other causes. It has been found that a 

 greatly increased wind-velocity usually precedes or 

 accompanies the immediate beginning of a thunder- 

 storm ; and it is suggested that the diminished press- 

 ure which has been found by Dr. Ferrari in front of 

 thunder-storms is due to the dynamic action of the 

 wind on the barometer or its environment, something 

 like the action of a SprengeLair-pumj). 



There yet remains, however, to be explained, the 

 rise in pressure during thunder-storms. There are 

 a number of reasons for believing this not due to a 

 lower temperature or falling rain. Professor Wil- 

 liam Ferrel, in conversation, suggested that this 

 also was a dynamic effect of the wind, and was due 

 to a reactionary effect of the sudden exj)ansion of the 

 air ascending in thunder-storms, something like the 

 recoil which takes place from the sudden expansion 

 of ignited powder. There are undoubtedly very rapid 

 moving currents of air in thunder-storms, and it may 

 well be that their sudden expansion or collision pro- 

 duces the effect in question. 



