of Edinburgh, Session 1877-78. 
567 
per cent., and left a white crystalline substance, soluble in water, 
alcohol, and ether. The authors are at present engaged in the 
investigation of this product. 
3d, The oxalate is obtained by treating the iodide with oxalate 
of silver. It crystallises, with one molecule of water, in clear 
hygroscopic plates. 
Analysis gave the following results : — 
I. II. Calculated. 
C, 36-95 36-78 36-93 
H, 7-87 7-89 7-69 
On carefully heating the salt to 110° C., the water of crystal- 
lisation is given off. At 146° C. the anhydrous salt decomposes 
into sulphide of methyl and pure oxalate of methyl — 
[(CH 3 ) 3 S] 2 C 2 0 4 = 2(CH 3 ) 2 S + (CH 3 ) 2 C 2 0 4 . 
The chromate and the iodate of trimethyl-sulphine were also pre- 
pared. Heated to about 140° C. they both fuse, and almost 
immediately explode. 
5. Extracts from two Letters by Professor Quincke on the 
Eefractive Indexes of Glass and Quartz, as tested by 
Reflection from the Surface. Communicated by Sir 
William Thomson. 
In answer to your question about the alteration of surface in 
quartz crystals, I place the glass or quartz 
plate whose refractive index y is to be 
determined between two right-angled flint- 
glass prisms, with oil of cassia, and measure 
the angle 0, at which total reflection begins 
from the hypothenuse of the first flint-glass 
prism ; the angle 0 can easily be calculated 
from i , /x the refractive index of the flint- 
glass, and P the angle of the prism. Sunlight 
falls from a collimator with a slit upon the 
system of flint-glass prisms, and after passing 
through the second prism is examined by a direct vision set of 
