M. C. Lea on Reactions of Gelatine. 81 
consisting of certain definite refrangibilities only, as is the case 
with the light of these nebula, is known to be emi 
uch gaseous masses would be doubtless, from many causes, 
unequally dense in different portions; and if matter condensed 
into the liquid or solid state were also present, it would, from 
its superior splendor, be visible as a bright point or points within 
the disk of the nebula. These suggestions are in close accord- 
ance with the observations of Lord Rosse. 
Another consideration which opposes the notion that these 
nebule are clusters of stars is found in the extreme simplicity 
of constitution which the three bright lines suggest, whether or 
not we regard these lines as indicating the presence of nitrogen, 
hydrogen and a substance unknown. 
with which the line in the nebule coincides, differs from that of 
origin of this difference of character observable among lines of 
the same element. May it not indicate a physical difference in 
the atoms, in connexion with the vibrations of which the lines 
are probably produced? The speculation presents itself, whether 
the occurrence of this one line only in the nebula may not in- 
dicate a form of matter more elementary than nitrogen, and 
which our analysis has not yet enabled us to detect. 
Art. X.— Reactions of Gelatine; by M. Carey Lua, Philadelphia. 
? 
stitutes, I believe, the first colored reaction described as pro- 
between pure gelatine and a perfectly colorless reagent. 
It is true that the precipitate produced in gelatine solutions by 
tannic acid is much deeper in color than the precipitant. 
t the straw-yellow color of gallotannic acid naturally leads to 
Am. Jour. Sc1.—Szconp Serres, Vou. XL, No. 118,—JuLy, 1865. 
Il 
