SCIENTIFIC SUMMARY. 
409 
Sulphuric acid 
Peroxide of iron 
Oxide of manganese ... 
Gypsum and other substances 
Water 
25-52 
40-00 
a trace 
23-81 
14-G7 
From the above table it will be inferred that this mineral is no longer to 
be regarded as being (what even the last edition of Dana’s Mineralogy 
states) a phosphate. It has a formula analogous to that of Apatelite. — 
Comptes Rendus , February 1st. 
Densities of the various Forms of Zircon. — M. A. Damour read a valuable 
paper on this subject, before a late meeting of the Academy. From a 
series of analyses he is led to infer that the differences in densities are not 
due to differences in chemical composition, but are rather the results of 
special molecular conditions. The variation in density extends from 4-04 
to 4-67, and is well illustrated in the interesting tables which accompany 
his paper. He concluded by stating that the question was one of geologic 
interest, for it is remarkable that the Zircons of syenitic and basaltic rocks 
have always a high density. This mineral has been artificially formed by 
acting on Zirconia with fluo-silicic acid. — See Comptes Rendus , January 
A New Stand for a simple Microscope has been devised by Mr. Richard 
Beck. The stage supports a revolving disk on which the object is placed, 
and the arrangement is such that, while the magnifier remains in one 
position, the object car. be turned so that it may be viewed in every aspect, 
losing nothing in point of illumination, although its position is altered. 
It is accompanied by a concave mirror and a condenser, and moreover is so 
contrived that the case which contains it leaves, room for the enclosure of 
a good sized box, for dissecting instruments and apparatus. By means of a 
very simple prismatic arrangement this instrument may be made binocular. 
— See a Paper read before the Microscopical Society, and printed in the 
Microscopical Journal for January, 1863. 
New Microscope for the Use of Families. — An instrument which is 
intended for family use has been constructed by Mr. Samuel Highley, of 
Green-street, Leicester-square. It is certainly of its kind, and considering 
the price at which it is sold, the best of all the cheap microscopes which 
we have seen. The annexed cut gives a better idea of the general form of 
the instrument than any words of ours could convey. It is so contrived, 
that when ready for use it is inclined at a fixed but convenient angle, and 
by reason of its attachment to the case which carries it, combines simpli- 
city of structure (no mean advantage to the amateur) and portability. It 
is not provided with a rack movement, but, like Messrs. Smith & Beck’s 
“ Educational,” the body slides with extreme ease and uniform telescopic 
motion, which allows the object to be readily brought into view; the 
accurate focus is then obtained by Dr. Beale’s method of draw-tube fine 
18 th, 1864. 
MICROSCOPY. 
