48 PROCEEDINGS OF SOCIETIES. 
LireRAry and PriLosopnicatn Socrery, MANCHESTER. 
MICROSCOPICAL SECTION. 
Annual Meeting, May 18th, 1863. 
A. G. Larnam, Esq., in the Chair. 
The annual report of the section for session 1862-63 was 
read, and officers appointed for the ensuing session. 
A communication on “ The Structure of the Cotton Fibre,” by 
Mr. Charles O’ Neill, F.C.8., was then read, in which the author 
states that chloride of zinc, as neutral as it could be made by 
digesting with metallic zinc, and also diluted sulphuric acid, would, 
under favorable circumstances, exhibit all the phenomena de- 
seribed by the author in his first communication. Chloride of 
zinc, however, required to be heated to its boiling-point, and 
sulphuric acid appeared very capricious in its action, The ap- 
pearances produced by these reagents lead him to the same con- 
clusions with regard to the structure of cotton; but he is more 
decidedly of opinion than he was before, that the so-called medul- 
lary matter is in reality a shrunk membrane similar in appear- 
ance to the membrane in dried quills. Finding that all known 
solvents of cotton gave the same appearances, Mr. O’Neill tried 
the action of solvents on gun-cotton, and found a further confir- 
mation in the action of ether upon it. 
It is well known that there art two modifications of gun-cotton, 
one soluble, the other insoluble in ether; but the author finds 
three varieties—(1) soluble in ether, but insoluble in ammoniuret 
of copper; (2) insoluble in ether, but soluble or dilutable in 
ammoniuret of copper; and (8), perfectly unacted upon either 
by ether or ammoniuret of copper. Operating on the first variety 
on the stage of the microscope with ordinary ether, it is almost 
instantly dissolved, with no evidence of structure, until, after a 
while, careful observation shows some remains of spiral vessels. 
By gradually diluting the ether with alcohol, the action is slackened 
until a point is arrived at when exactly the same phenomena are 
produced as by the copper solution. About two thirds ether and 
one third alcohol was found to be a suitable mixture; but this 
will evidently vary with different preparations. 
Mr. O’Neill considers the number of turns of one spiral to be 
certainly not greater than from 1100 to 1300 in the inch, and 
generally much less than. this, the mean of many countings run- 
ning between 600 and 700 for the contracted fibre. 
Mr. A. G. Latham made the following communication :— 
It may be remembered that some few months ago I proposed to 
this section as a subject for discussion, “The Causes of the 
Metallic Lustre of the Scales on the Wings of certain Moths.” 
I then suggested that the metallic markings, and lustre of the 
