106 Scientific Intelligence. . 
metal attached to the tube. The edges of the slit must be ground per- 
fectly true. 
This apparatus does not require a darkened chamber or delicate and 
difficult. adjustments. It answers equally well for observations on the 
solar spectrum, on the absorption lines of liquids and gases, on the elec- 
tric spectra of Masson and Pliicker, and on the chemical lines of Kirch- 
and Bunsen.—Pogg ii w. G. 
Note.—This apparatus is constructed in New York by Mr. Charles 
Sacher, under my direction, the prism being supplied by Mr. Henry Fitz, 
the well-known optician. The price of the instrument complete with an 
equilateral flint glass prism, is 
4, } 
on the Physical con 
TynpALL has communicated an important and interesting paper on the 
brass tube 2°4 inches in diameter and divided into two compartments, a 
and 6. The portion @ is destined to receive the gases and vapors; it 3s 
the cube C, to the tube a, the chamber d is partly surrounded with an 
annular space in which cold water circulates. 3. Of a thermo-electric 
the tubea. 4. Of asecond cube C’ also filled with boiling water and the 
rays from which fall upon the second face of the pile. Between the cube 
C’ and the adjacent surface of the pile, a screen is placed, which may be 
moved backward and forward, so as to make the two sources of heat 
exactly neutralize each other. A vacuum is then made in the tube a, and 
the chamber 6, and the needle of the galvanometer is brought exactly to 
