192 



NATURE 



[February 2, 



ever known of animals so directly opposita in their dis- 

 positions forming an attachment of such singular nature. 

 Their beautiful and interesting progeny are most admir- 

 able productions of nature. The group is truly pleasing 

 and astonishing, and must be witnessed to form an ade- 

 quate idea of them. The remarkable instances of sub- 

 dued temper and association of animals to permit the 

 keeper to enter their den, and to introduce their perfor- 

 mance to the spectators, is the greatest phenomenon in 

 natural history." 



V. Ball. 



OBSERVATIONS OF ATMOSPHERIC 

 ELECTRICITY IN AMERICAN 



'T^HE meteorological official of the United States 

 -*■ known as " The Chief Signal Officer" has sanctioned 

 the publication of this voluminous report of 320 quarto 

 pages, embodying the result of a widespread photo- 

 graphic record and direct reading of atmospheric electro- 

 meters carried out under the auspices of the United States 

 Government during the years 1884 to 1888, with the 

 immediately utilitarian object of ascertaining how far it 

 was possible to use electrical indication in weather pre- 

 diction. As Mr. Mendenhall says, " No studies or inves- 

 tigations which did not bear upon this question were 

 [considered] proper or allowable." 



Although thus limited in scope the actual observations 

 made and here recorded can hardly fail to be of service 

 to future investigators into this obscure subject. 



The report begins with a historical introduction, in 

 which it is admitted that electricity was first purposely 

 drawn from the clouds in France by Buffbn and 

 D'Alibard about a month before Franklin tried his already 

 projected experiment ; and that de Saussure was one of 

 the first to obtain fairly quantitative results and to detect 

 a diurnal period. 



Volta " hit upon the capital device of a burning match " 

 to replace the previous feeble collecting devices such as a 

 bullet and wire shot up into the air. But nothing really 

 exact and continuous was done " until Sir W. Thomson 

 attacked the problem." He introduced the quadrant elec- 

 trometer and the water-dropper, which have been the 

 universal recording instruments ever since. 



In fact " the work of Palmieri on Mount Vesuvius 

 constitutes perhaps the only extensive series of observa- 

 tions in which instruments founded on the original design 

 of Sir W. Thomson have not been used." 



In the States the first energetic and influential mover 

 in the direction of a serious record appears to have been 

 Prof. Cleveland Abbe, who got himself authorised in 

 1 880 by the Chief Signal officer to consult with Prof. Row- 

 land on the subject, and afterwards with Prof. Trowbridge, 

 and to make arrangements for a series of effective obser- 

 vations. Under the auspices of these gentlemen a staff" 

 of observers were trained and suitable instruments 

 obtained, tested, and improved. Various collectors were 

 tested, and in 1883 a photographic registration appara- 

 tus of M. Mascart was put into operation. In 1884 Mr. 

 Mendenhall " was appointed to assume the direction of 

 the work as chief of the physical laboratory and in- 

 strument division of the office in Washington." Stations 

 were established in Washington, Baltimore, Boston, New 

 Haven, Ithaca, and Ohio. 



Much work was done in connection with electrometers 

 by McAdie and McRae, but this is incorporated in the 

 article " Electrometer " of the " Ency. Britt." 



The instrument ultimately adopted was a quadrant 

 electrometer of the Mascart pattern with special improve- 

 ments, and was constructed by the Soci^td Gdnevoise. A 

 picture of it is given. 



1 " Report of Studies of Atmospheric Electricity." By T. C. Mendenhall. 

 Extract from Memoirs of the National Academy of Sciences, 1889. 

 (Wasiiington.) 



The method of connecting the quadrants to the two 

 equal halves of a water battery, so that they might always 

 be at equal opposite potentials, and of attaching the 

 needle to the collector, was after many trials adopted ; 

 partly because higher insulation was thus possible, partly 

 in order to get a straight line law. Deviation from this, 

 due to what is called the "electric directing couple," is 

 not overlooked, but by a stiff suspension and small range 

 it is minimised. 



An interesting chapter is that on " collectors." The 

 water-dropper was mostly used, but its freezing is apt to 

 interrupt the record. " Sergeant Morrill experimented 

 on a special flame collector," supplied with gas at con- 

 stant pressure and arranged so that wind could not ex- 

 tinguish it, and "before the termination of the work 

 obtained very satisfactory results." But in order to secure 

 uniformity between different stations he also designed a 

 mechanical collector — a clockwork machine with revolv- 

 ing arm and intermittent contacts, which is virtually a 

 gigantic replenisher, utilising the atmospheric potential 

 as an inductor, and thereby feeding the electrometer up to 

 the same potential. It seems to be as quick in response 

 as a water-dropper (an important point, as some of the 

 fluctuations of potential are very rapid), but "as it was 

 only completed towards the end of the period of observa- 

 tion nothing very definite can be said of its performance." 

 An illustration of the ingenious device is given in detail. 



Observations. 



Preliminary records are given showing the curves got 

 at a roof station and a balcony station, also at diff"erent 

 observatories in the same town. Some also from the top 

 of the Washington Monument, which naturally show far 

 greater potential and changes than the instrument in the 

 Signal Office. 



There are plotted a number of zigzags obtained from 

 the different stations about the States, and very compli- 

 cated and entangled the record is. None of the stations 

 show any agreement ; and, particularly at Ithaca, the elec- 

 trometers seem usually to have been in a wildly excited 

 state. 



But during an Aurora on May 20, 1888, they were singu- 

 larly quiet, and the remark is made : " It will be observed 

 that the indications of the electrometer were positive 

 during the day and night, and that no unusual fluctuations 

 occurred." 



The atmospheric potential is usually positive, and it 

 has been often thought that a change to negative signal- 

 ised bad weather. Certainly this does frequently happen ; 

 sufficiently often to make it worth while specially to 

 examine this point ; and several curve charts are given to 

 show that "negative electricity in clear v/eather was 

 observed at most if not all of the Signal Service Stations 

 on numerous occasions during the progress of the work. 

 In many cases precipitation occurred at points 10 to 100 

 miles distant, but in others clear weather prevailed over 

 almost the entire country. A number of instances of 

 negative potential during clear weather occurred at Ithaca, 

 where careful attention was given to the matter of special 

 observation by Mr. Schultze." 



Effect of Dust, Haze, Fog. 

 " The eff'ect ©f dust, haze, smoke, &c., in producing 

 negative potential has been noticed by more than one 

 observer. [Query whether the negative potential can have 

 ever produced or permitted the haze. — O. J. L.] Several 

 instances of the action of clouds of dust were noted by 

 Sergeant Morrill at Boston. On March 7, 1888, in the 

 afternoon the potential was observed to fall rapidly from 

 - 90 to - 270 upon the rising of an especially heavy cloud 

 of dust, and similar phenomena were observed on 

 April 7." "A fall of potential could be certainly predicted 

 when a dust cloud was seen rising. On other days when 

 high winds and dust clouds prevailed negative potential 



NO. I 2 17, VOL. 47] 



