Geology and Natural History. 55 
urement was made we different thicknesses from 20°25 mms. to 
4°37 mins, and showe at the number of vibrations was nearly 
proportional to the pa A fork three decimeters long was 
then shortened 20 mms. at a time and the vibrations measnred in 
each case. The length ‘of the prong being altered from 295 to 57 
mms., the number of vibrations increased from 40 to 9 974. Hence 
the vibrations are inv ersely proportional to the square of the serra. 
calling the latter the projection of the line bisecting the prot 1B) 0 
the axis plus a small quantity y, which in this case equalled 3 
mms. These laws may be written in the form of the a al 
€ . . é eee . 5 
iby)? in which n is the number of vibrations, e the thick- 
ness, 2 the length, y a small constant, and A a constant depending 
on the material. For steel, =818270. To co mpare this con- 
stant with theory, A was computed from the formula for the 
number of vibrations of an elastic bar in terms of v, the velocity of 
sound in it; ee v=4985 m., according to the’ Lah PDE os 
Werthatne’ : ’ Kin this case became 820131, a result differi 
that aedettire obtained by only a fifth ‘of one per sai "The 
number of vibrations of three fink were found by measurement 
to be 144 ‘7, 77°7, 29°7, and by the formula 146-4, 79°0, 29-0. Hence 
forks may be made by calculation to give any desired number of 
agenda within one or two per cent.—- Comptes Rendus, ae 
01 i 
5. “Polarization of Light ; by Witita Srorniswoone, pra e: 
LL.D., F.R.S. 130 pp. 12mo. London: 1874. Nature "Series. 
(Macmillan & Co.)—This small treatise ‘on ae Polarization of 
Light, as the Preface states, contains the substance of lectures de- 
livere d by the author at various times to his work-people, and 
t 
ple manner, and are well illustrated by means of two seetchicns 
colored plates, besides a number of Rak eng 
II. GroLtoagy anp NatTuRAL History. 
1. Evrthquakes of North Carolina.—An excellent article on 
earthquakes in the mountain region of North Carolina has been 
published by Hon. T. L. Clingman i in the Western Expositor of Ashe- 
Ville ,N He states that more than thirty years since his at- 
tention was called to statements that a mountain in the northern 
oo aywood Coun nty was shaken at intervals of two or three 
years; and in 1848 he visited the region rat published a paper 
on it. The principal facts stated were the 
Between the Blue Ridge, which in N aoe Cuchi separates the 
waters falling into the Atlantic from those discharged into the Mis- 
rane er ‘the great chain on the Tennessee border designated in 
se y such names as Iron, Unaka, and Smoky, there is an 
elevated plateau of over two hundred miles in length, with an 
average breadth of fifty miles. The beds of the larger streams 
