Friedel and Crafts on the Combinations, ete. 307 
is put in its place; the diatom stage raised until the hair, with 
the diatom on it, is in contact, when the diatom is taken off by 
the moisture that has been previously breathed upon the slide. 
The superiority of the contrivance here described is its sim- 
plicity and absolute steadiness. 
n the drawing, the position of the spring G with the cork- 
holder N is reversed. They turn, as already described, in any 
direction, horizontally. 
The facility with which a diatom may “be handled,” to use 
the term in this connection, is one of the great advantages of 
- Zentmayer’s contrivance. The point of the hair may be 
brought into focus along side of the diatom, which may then, 
y using the screws of the mechanical stage, be pushed in any 
direction by the finger, and separated from the mass, or, when 
transferred to a clean slide, may be placed wherever required 
thereon. With such an instrument may be understood the 
modus operandi by which the 892 diatoms of “ Moller’s Diato- 
maceen platte” were arranged. 
Nothing more has been attempted here, than to describe the 
particular instrument. But no one can understand the whole 
subject, without reading the most admirable article of Mr. H. 
L. Smith already referred to, and which set the writer to work 
to improve, if possible, the mechanism there described. _L. 
Agr. XXXIL—The Combinations of Silicon with Alcoholic Radi- 
cals; by C. FRIEDEL and J. M. Crarts.* 
IN a previous research+ we studied the ethers of silicic acid, 
and discovered a number of new bodies, whose structure leads 
e conclusion that the atomic weight of silicon is 28, and that 
the formula of silicic acid is SiO,. Gaudin, and afterwards 
Odling, first gave silicon its true atomic weight, and silicic acid 
bas emical gr on 
Wanting to establish completely the correctness of their A 
d a large number 0 the ee authorities in chemistry have 
F that the chemical properties of silicates can only be expla 
‘ adopting the ce to 
*The chemical symbols used have the values which belong to them in the new 
+t This Journal, I, xliii, pp. 153 and 331; Ann. de Chim. et Phys., IV, ix, p. 5. 
