122 Progress in Science. [January, 
Captain F.,H. Lang and Mr. Tatem, of Reading, give a mode of re-mounting 
or sele@ing diatoms from slides already mounted in balsam. The balsam- 
mounted slide is placed upon a hot plate, and when sufficiently heated, the 
cover is removed by means of a needle. The diatoms will either be on the 
slide or the cover, according to the mode adopted in mounting. Apply at once 
while upon the hot plate a drop of turpentine, remove the slide to the stage of 
the disse@ting microscope, and add more turpentine. Have ready a clean slip 
of glass, on which has been placed a drop of turpentine. In the case of large 
discoid and other forms, having applied plenty of turpentine, they can easily 
be transferred by means of a fine sable-hair brush from the original slide to 
the pool of turpentine on the clean one. In the case of the finer forms, it is 
better to place less turpentine on the original slide, colleé the diatoms into a 
heap, allow the turpentine to dry a little, and then by a twist of the brush to 
transfer them en masse to the new slide. In either case, having got them 
there, push them together and mop up the superfluous turpentine, and then, 
still under the dissecting microscope, slant the slide by placing a piece of 
folded paper under one end, and apply a little benzole by means ofa clean brush 
or glass rod, immediately above them, that is, on the end of the slide that is 
raised, and allow it to float gradually overthem, care being taken that it does 
not flow with too great a rush and carry away the diatoms with it. Repeat 
this process some half-dozen times, till the whole of the turpentine and balsam 
has been washed away, and till the valves are left dry and black after the 
benzole is evaporated. They can then be transferred in the usual way to any 
other slide.* If gum has been used to fix the diatoms, it may be found that 
some of the valves, especially the discoid ones, remain obstinately adherent to 
the glass after the turpentine has been placed over them. In such a case the 
process as above detailed must be carried out on the original slide, and then, 
after the benzole is thoroughly evaporated, water must be applied two or three 
times in the same way as the benzole, for the purpose of washing away the 
gum and freeing the diatoms, which can then, when dried, be lifted one by one 
and transferred in the usual manner. By this simple and easy mothod, 
selections can be made from balsam-mounted slides of any particular valves 
required, and spoilt and unsatisfactory mounts re-set.t+ 
Mr. Browning has prepared four series of objects for the micro-spectroscope. 
The first three consist of fluids in sealed tubes; one set of twelve being 
devoted to chemical solutions; the second, a similar number of colouring 
matters from vegetable sources, and the third set of six illustrates blood 
compounds. The remaining collection consists of various blowpipe beads and 
crystals. They are accompanied by a catalogue giving brief directions for 
viewing them, and also a short explanation of the use of the various micro- 
spectroscope apparatus constructed by Mr. Browning. In the absence of a 
manual on the use of this important addition to the microscope, the specimens 
and directions will be of great service to those commencing such studies. It 
is much to be desired that some competent person would undertake a practical 
work on the micro-speétroscope, as nearly all the information at present 
published is contained in various scattered papers. 
““ The Monthly Microscopical Journal” for September contains a paper by 
Mr. H. C. Sorby, on ‘‘ The Examination of Mixed Colouring Matters with the 
Spectrum-Microscope.” It forms a valuable sequel to many other contribu- 
tions to a knowledge of the spectra of vegetable colours by the same author, 
and consists chiefly of observations on various Alg@. The subjecé is too 
elaborate to admit of an abstra&. Inthe same Journal is also ‘*An Account 
of the Spectra formed by the Passage of Polarised Light through Doubly 
Refradting Crystals seen with the Microscope,” by Francis Deas, M.A., LL.B., 
F.R.S.E. 
Mr. H. G. Bridge communicates to the ‘“‘ Monthly Microscopical Journal ” 
for November some remarks on the mode of mapping speétra with the 
“ Bright Line Micrometer,” adapted by Mr. Browning to the micro-spectro- 
* Quarterly Journal of Science, vol. i. (N.S.), Pp. 276. 
+ Monthly Microscopical Journal, vol. vi., p. 217. 
