Physics and Chemistry. dl 
4, Density of the Earth—Pu. v. Jouty has employed the 
balance to directly determine the density of the earth. A body 
was weighed in two stations distant 21:005™ vertically from each 
oth The errors incident to this method were examined and 
the value obtained for the earth’s density was p=5°692. The re- 
sults obtained by previous observers are as follows: 
Muskelyne soo SU ct cee we eres Mane 4°713 
Cavendish ...2 22.22... 5°48 
Reich TERT vid 1, 
. Baily 5°66 
A. Cornu and J. B. Baille 5°56 
Cath... ee ae oe ABST 
Airy Mineo ihe ae 5°480 
—Annalen der Physik und Chemie, No. 10, 1881, p. 331. J.T. 
na new arrangement for sensitive flames ; uORD Ray- 
LEIGH.—A jet of coal gas from a pin-hole burner rises vertically 
in the interior of a cavity from which the air is exciuded. It then 
passes into a brass tube a few inches long, 
top, burns in the open air. The front wall of the cavity is formed 
of a flexible membrane of tissue paper, through which external 
sounds can reach the burner. 
If the extreme of sensitiveness be aimed at, the gas pressure must 
f : ; ; : b sound’ 
he apparatus exhibited was made in Prof. Stuart’s workshop. 
An adjustment for directing the jet exactly up the middle of the 
brass tube is found necessary, and some advantage is gained by 
contracting the tube somewhat at the place of ignition.— Cam- 
bridge Phil. Soc., Noy. 8, 1880. 
6. On an effect of vibrations upon a suspended disc ; by Lorp 
Rayieteu.—tIn the British Association experiment for determining 
the unit of electrical resistance, a magnet and mirror are enclosed 
in a wooden box, attached to the lower end of a tube through 
which the silk suspension fiber passes. Under these circumstances 
it is found that the slightest tap with the finger-nail upon the box 
deflects the mirror to an extraordinary degree. The disturbance 
appears to be due to aerial vibrations within the box, acting upon 
the mirror, We know that a flat body, like a mirror, tends to 
