Scientific Notes. 
*43 
1878.] 
be obtained in the course of a few moments. If pieces of charcoal, slightly 
incandescent, are put in this jet they inflame spontaneously with great violence. 
M. Pidtet has already announced his intention of attempting the condensation 
of hydrogen and nitrogen by means of a similar apparatus to that we have 
described We shall hope to give the results of his further experiments 
in a future number of this Journal. Meanwhile we would refer our readers 
to the “Chemical News” of January 4 for a detailed description and 
diagrams of the complicated apparatus, by means of which M. Pidtet has 
succeeded in liquefying oxygen. 
Mr. Charles Stodder, in the “ American Journal of Microscopy ” (vol. ii., 
page 142), recommends the use of chloroform as a preparation for 
mounting dried Algae in balsam. The immersion in chloroform has the 
effedt of restoring the Algae to their natural shape : the portions seledted are 
then placed on a slide, and just before the chloroform evaporates the balsam 
is dropped on, and the objedt covered in the usual manner. The balsam 
should be allowed to harden slowly, as if heat is applied the specimen is liable 
to be shrivelled. The process is of especial value in mounting diatoms 
in situ. 
The “American Journal of Microscopy” (vol. ii., p. 129) contains some 
remarks on the examination of objectives, by Ernest Gundlach, which may 
prove interesting to microscopists. The way in which various forms of 
spherical and chromatic aberration render themselves apparent are familiarly 
described. The subjects of angular aperture and working distance are dis- 
cussed, and it is shown that considerable resolving power is only obtainable 
at the sacrifice of some portion of the latter quality of the objective. The 
immersion system is shown to be a substitute for the extreme thickness of the 
front lens needed in correction, formed by a corresponding stratum of water, 
to gain with the highest performance a tolerable working distance. 
Our readers have probably noticed a recent addition to our fictile manufac- 
tures of a number of ornamental vases, cups, bowls, &c., of clear white glass, 
covered with beautiful iridescent films of different colours. At first it was 
thought that the process consisted in submitting the glass to the action of a 
deoxidating flame, and that the colours were caused by the reduction of the 
lead ; from the specification of the patent, however, we find that the inventor 
of the process is M. L. Clemandot, a French civil engineer, who has patented 
it in France, England, and America, and that the principle of the process 
consists in submitting the glass vessels to the action of dilute hydrochloric, 
sulphuric, or other acid, under a pressure of from two to six atmospheres. M. 
Clemandot claims to be able to imitate the beautiful nacreous films on 
ancient glass which has been submitted to the combined action of air and 
water for tw® or three thousand years ; but the ornamental vessels already 
exhibited, although very pretty, are a long way off the poorest specimens of 
Assyrian or Egyptian glass in any ordinary collection. Time is evidently an 
important factor in bringing about this singular change. 
The injurious influence of the products of combustion of coal-gas upon the 
leather bindings of books is only too well known. Vellum seems unaffected ; 
morocco suffers least ; calf is much injured, and Russia still more so. The 
disintegration is most rapid with books on the upper shelves of a library, 
whither the heated products of combustion ascend, and where they are 
absorbed and condensed. By comparing specimens of old leather with 
specimens of new it is quite clear that the destructive influence of gas is due 
mainly to its sulphur. True there are traces of sulphates in the dye and size 
of new leather bindings, but the quantity is insignificant, and there is prac- 
tically no free sulphuric acid. That leather may be destroyed by the oil of 
vitriol produced by the burning of gas in a library is proved by the following 
observations and analyses of Prof. A. H. Church, of the Royal Agricultural 
College, Cirencester. The librarian of one of our public libraries forwarded 
to him the backs of several volumes which had been “ shed ” by the books 
on the upper shelves in an apartment lighted by gas. The leather of one of 
these backs (a volume of the “ Archasologia”) was carefully scraped off so as 
