244 



NATURE 



[Jan. 24, 1878 



and no doubt cones had been erected before the time of Cheops, 

 and had their meaning and uses. Probably they were first made 

 of earth, and the circular base would no doubt be set out by a 

 cord, as above described. Cheops, by hi; architect, squared the 

 circular base, getting thereby lines much better adapted to stone 

 work, whilst still keeping the old sacred emblem, though in a 

 developed form. It may, I believe, be traced down to many 

 modern forms not often suspected of bearing any relation to it. 

 Belper, January 17 J. G. Jackson 



Acoustical Effects of Atmospheric Pressure 



On tapping an ordinary bell-jar receiver after exhaustion, the 

 following was noticed. The note derived from percussion after 

 exhaustion was sensibly of a higher grade than that obtained 

 from the glass containing air. On gradually letting the air in, 

 the note sank directly as the amount of air so introduced. We 

 conclude that the phenomena here recorded are connected with 

 the atmospheric pressure, and that the note yielded is a function 

 of the atmospheric pressure. Can any of your readers suggest a 

 method for the investigation of the observed facts, if no investi- 

 gations have been before made on the subject. 



Rugby, January 19 G. Rayleigh Vicars 



TRANSATLANTIC LONGITUDES^ 



IT will be remembered that a preliminary account of 

 the results of the transatlantic longitude determina- 

 tion of 1872 was published in Vol. xxii. of the Proceedings 

 of the American Association for the Advancement of 

 Science. We have now received the final report of Mr. 

 Hilgard, which embodies not only the results, but also the 

 observations, and which sets forth concisely the manner 

 in which the former were deduced from the latter. 



The importance of fixing with the greatest precision 

 achievable, the longitude of some point in the coast survey 

 triangulation with reference to Greenwich, led the U.S. 

 Government promptly to make use of the means afforded 

 by the completion of the Atlantic telegraph cable from 

 Ireland to Newfoundland. 



The first telegraphic longitude determination through 

 it, made under the direction of Dr. B. A. Gould, in 1866, 

 although it surpassed in exactness all results obtained by 

 different methods was subject to a small but indeterminate 

 correction, the " personal equation " between the American 

 and the standard Greenwich observer. 



Use was therefore made of the French cable in 1870 to 

 make another determination under different circumstances, 

 and under the charge of Mr. Dean the longitude difference 

 between Brest and Cambridge, U.S., as before, was obtained ; 

 but as at that time no cable was in operation between 

 Brest and England, the connecting link, Brest- Greenwich, 

 remained undetermined until 1872, when Mr. Hilgard 

 took charge of the work necessary to supply this deficiency, 

 and since the opportunity was afforded, to repeat the 

 Transatlantic determination. This time an intermediate 

 station, St. Pierre, on the American side, was introduced, 

 thus varying still more the conditions under which this 

 third determination was made. 



The general plan of operations was to unite at Brest 

 time signals from St. Pierre, Greenwich, and Paris. The 

 co-operation at the last-named stations of the Astronomer- 

 Royal, Sir G. B. Airy, and of M. Delaunay, and the 

 generosity of the telegraph companies, enabled Mr. 

 Hilgard to finish the work successfully in September of 

 that year. 



We can only advert briefly to one or two points of 

 interest. The accordance of the results appears to have 

 been due in a great measure to the attention given to the 

 accurate determination of the relative personal errors of 

 the observers, which gave also indirectly the " personal 

 equation " correction, lacking in the longitude determina- 

 tion of 1866. 



■i Final Report on the Determination of 1872, with a Review of Previous 

 Determinations. By J. E Hilgard. From the United States Coast Survey 

 Report for 1874. 



Incidentally, the "wave-time" of the cable signals was 

 deduced, and on the assumption of equality in time in 

 either direction, the resulting wave-time from Brest to St. 

 Pierre, through a length of cable equal to 2,979 statute 

 miles, is given as os.*35i ± s.'oo3. 



The final results are given as follows, and the author 

 remarks " that the close agreement of the three indepen- 

 dent determinations made in different years is no less 

 surprising than it is satisfactory." Even if we assume, as 

 Mr. Hilgard evidently does, the identity of the results as 

 accidental within the limits of the probable errors assigned, 

 the determination must be characterised as being of the 

 highest order of precision. 



Longitude of Cambridge {^Harvard College Observatory dome) west 

 of Greenwich {meridian) : — 



h. m. s. s. 



1866 4 44 3099 J- OTO 



1870 30 98 -t o -06 



1872 30 98 J- 0-04 



Mean 



4 44 30"98±o-04 



Referring this mean value to Paris (meridian of France) 

 we have : — 



Cambridge — Paris ... 4h. 53!n. 5is"9S ± os. -06 



These results, combined with elaborate determinations 

 of the longitude difference, Washington-Cambridge, 

 give :— 



h. m. s. s. 



Washington (Naval Observatory) 



— Greenwich 5 8 12-09 ± 0*05 



Washington (Naval Observatory) 



—Paris 5 17 33"o6±oo7 



We may, therefore, consider the geographical position 

 of the Washington Observatory as one of the best deter- 

 mined in reference to others. 



One of the incidental but highly important results of 

 this expedition is the longitude difference Greenwich- 

 Paris, the accuracy of which was checked by the condi- 

 tions involved in the closing of the longitude triangle 

 Greenwich-Paris-Brest. The result, 9m. 20s.'97 must 

 now supersede the value obtained by Mr. Leverrier in 

 1854, which it exceeds by nearly half a second. 



ANTOINE CESAR BECQUEREL 



IT is with regret that we record the death of the noted 

 French physicist, Prof. Becquerel, which occurred on 

 January 18, in Paris. Antoine Cesar Becquerel was born 

 at Chitillon-sur-Loing, in the Loiret department, March 8, 

 1788. After completing a course in the Paris Polytechnic, 

 he entered, in 1808, the Imperial Engineer Corps. It 

 was no time of idleness for young officers, and he was 

 shortly in active service, taking part in the entire Spaiash 

 campaign under General Luchet. Here he was present 

 at the sieges of Torbosa, Tarragona, Lagonte, and Va- 

 lencia, and manifested such marked abilities that in 1812 

 he returned to Paris to receive the rank of captain, and 

 be presented with the Cross of Chevalier of the Legion of 

 Honour, from Napoleon's own hands. In the following 

 year he was sent by the Emperor to complete the fortifi- 

 cations on the German frontier. At the fall of the 

 empire, in 181 5, he resigned his position as chief of 

 battalion in the Engineer Corps, and devoted himself 

 exclusively to physical and chemical research, accepting 

 a position as teacher in the Muse'e d'Histoire Naturelle, 

 of Paris. In 1837 he was made professor in this insti- 

 tution and occupied this position up to the time of his 

 death. Shortly after entering upon his scientific career 

 he commenced the remarkable series of investigations in 

 electricity and magnetism which have been uninter- 

 ruptedly continued during the past half-century, and have 

 linked his name closely with every branch of these two 

 leading departments of physics. In thermo-electricity 

 Becquerel carried oat a large number of experiments on the 



