Fehiuaky 22, 1895.] 



SCIENCE. 



221 



photographic method of comparing the rate of vi- 

 bration of two tuning forks. The forks are 

 so clamped that a pron<>: of each is held in 

 front of a nianometric capsule. The forks 

 are bowed and the llauies photographed as 

 described in the Physical Review, Vol. 

 II., p. 305, 187.^. The vibrations arc then 

 counted in the wavj' line on the negative. 

 The accuracy in ordinary work is about two 

 or three-tenths of a \\ave per second. 



The second paper was by Prof J. K. 

 Rees on the Penumbne of .ntn-sj)ots as 

 shown in Rutherfui'd"s photographs, with 

 especial reference to the discussion at the 

 December meeting of the Royal Astronom- 

 ical Society. Professor Rees called the at- 

 tention of the Section to the remarks made 

 by the Rev. F. Howlett on presenting to 

 the Royal Astronomit'al Society of London 

 three volumes of sun-spot drawings. Tliis 

 set of volumes contains drawings made dur- 

 ing a period of thirty-five years, and shows 

 minute details in regard to the forms and 

 changes of solar spots. The Rev. Mr. How- 

 lett stated tliat his main object in continu- 

 ing the series had been to test the theoiy 

 put forth by Professor Wilson, of Glasgow, 

 in the latter part of the last century. "Wil- 

 son's theory claimed that the penumbra in 

 a spot shelves down toward the umbra ; and 

 that the portion of the penumbra nearest 

 the sun's centre will, therefore, grow nar- 

 rower and narrower, due to perspective, as 

 the sun-spot reaches a point nearer and 

 nearer to the limb. Mr. Howlett claimed 

 that Ivis drawings showed that the Wilson- 

 ian theory was not Ijoi-ne out bj' his obser- 

 vations as recorded in his drawings. 



He made bold to s;n' that, instead of the 

 penumbra of tlie spot possessing shelving 

 aides sloping down toward the umbra, the 

 penumbra shows a convex surface in a 

 curve conformable to the general contour 

 of the solar surface. He remarked that he 

 had not himself witnessed a single case of 

 certain notching of the limb. 



Professor Rees exhibited on the screen a 

 series of fine photogi-aphs of the solar sur- 

 face taken by Mr. Rutherfuid with his pho- 

 tographic telescope (1.3 inches diameter of 

 object gla.ss, 11 feet of focal length) during 

 the years 1870-1871. Attention was willed 

 to the appearance of the penumbral regions 

 of the spots which showed conclusively that 

 the penumbra was. as a rule, eccentric with 

 respect to the umbra. Spots were pointed 

 out near the centre of the sun where the 

 penumbral mai-king was deficient on, .some- 

 times the west side, then on the east side, 

 sometimes on the north side and sometimes 

 on the south side. Spots were also indi- 

 cated which showed, when near the limb of 

 the sun, the penumbral region wanting on 

 the side farthest from the centre and well 

 developed on the side toward the centre. So 

 far as these photographs showed, there was 

 no doubt that the A\"ilson theory did not 

 completely explain the various phenom- 

 ena. 



Professor Rees also showed some pictures 

 of sun-spots taken by Mr. C. A. Post, of 

 New York City, exhibiting the non-central 

 character of the umbra with respect to the pe- 

 numbra. Mr. C. A. Post, of New York City, 

 then threw on the screen some photographs 

 of the sun and moon that he had taken. 



He also exhibited a series of strikinglj- 

 beautiful lantern slides made from photo- 

 graphs of lightning flashes. 



Professor M. I. Pupin described his new 

 form of automatic vacuum-pump (see Am. 

 Journ. Sci., Vol. 3!), 1895, p. 10). An ex- 

 tremelj' ingenious device utilizes an ordi- 

 nary vacuum pump (water pump) to raise 

 mercury for tlu' Sprengel pump. Little 

 mercurj' is needed and the whole is con- 

 tinuous in its action. 



INDIAIfA ACADEMY OF SCIEXCE. 



The Indiana Academy of Science met at 

 Indianapolis, December 27-28, 1894, with 

 W. A. Noyes, of the Rose Polj'technic of 



