148 Application of the Microscope. . | \etrnal, Sept ii. 
The following is the diagnosis of the species :— 
Tricodectes tigris, sp. nov. Pale fulvous, head and thorax 
fulvous yellow, abdomen pale yellowish white, somewhat quadrate. 
Head transverse, vertex concave, with two trapeziform black 
spots in the centre, lateral margin situated before the eyes, a 
black spot at the anterior angle passing to the base of the antenne 
and uniting with the diagonal fasciz on each side of the occiput. 
Prothorax subconical smaller than the head. Metathorax 
transverse narrower than head, posterior margin concave ciliated. 
Abdomen broadly ovate, hairy. 
Antenne, front joint large, subcylindrical; second, smaller ; 
third, clavate and recurved. ‘Legs moderate, tibiz clavate ; ungues 
slender incurved. 
Length, 1:2 millimétre. 
Cuirton, 8rd August, 1870. 
VIII.—On the Application of the Microscope to the Study of Rocks. 
By H. C. Sorsy, F.RB.S., &e. 
I nave read with much interest Mr. Allport’s valuable paper “On the 
Microscopical Structure of Rocks and Minerals,” in the ‘ Monthly 
Microscopical Journal’ for August,* in which he says that the 
papers by myself and by Mr. David Forbes constitute, he believes, 
the extent of the published information on the subject. This may 
be almost true, as far as England is concerned, but is far from 
being absolutely correct. When I was in Germany, nine years ago, 
I strongly impressed on my friend Professor Zirkel the importance 
of the study of the microscopical structure of rocks; and when 
sitting on the top of the Drachenfels I described to him how thin 
sections were prepared, and advised him to apply himself to that 
kind of investigation. Iam very glad that he has most success- 
fully carried out my suggestion, and has already published many 
most excellent papers on the subject. His brother-in-law, Professor 
Vogelsang, has also taken up the inquiry, and published a separate 
work, besides some valuable papers. Professor H. Fischer has 
likewise studied the microscopical structure of minerals, and printed 
a very useful chronological list of all the papers published in various 
countries, which are connected with the application of the microscope 
to the study of mineralogy, petrography, and paleontology. 
I here subjoin a list of some of the more important publica- 
tions, for most of which I am indebted to the authors themselves, 
which will probably be useful to those interested in the subject. 
* Vol. iv., p. 98. 
