NOTES AND MEMORANDA. 
l-:!9 
of liny absorption band. An im2n-oved form of mioro-spectroscoije 
(designed and exbildted by Mr. F. H. Ward, M.E.C.S.), the im- 
provements being (1) quick movement of the slide carrying tbe slit, 
(‘.^) scale for registering tbe position of tlie slit, (3) arrangement 
for comparing three spectra, or for splitting a single spectrum and 
inserting a second spectrum between the halves, and (4) new form of 
comparison stage. 
The Soiree of the Chemical Society. — At this soiree, given by the 
President, Dr. Gladstone, F.E.S., at Burlington House, on May 30, 
there were exhibited : — A new arrangement of polarizing aj^paratus 
for the microscof>e, in which both the jiolarizing and analyzing jjrisms 
can be readily shifted out of the field, thus allowing the object to be 
viewed by direct illumination. Ap^jaratus for photographing plates 
of crystals (ordinary-sized microscopic objects enlarged to 3 inches) 
by means of polarized light (both exhibited by Messrs. Murray and 
Heath). 
A French view of the Binocular Microscope. — The ditference in the 
appreciation of the binocular microscope by microscopists in England 
and America on the one hand, and those of France and Germany 
on the other — in which latter countries Wenham’s prism, if not un- 
known, is at any rate almost wholly unused — is a phenomenon not 
easily to be accounted for. The following is the view taken of 
binocular microscopes by Professor Eanvier, of Paris, the leading 
histologist of the day, in his book, just published, on ‘ Practical 
Histology “ The binocular microscopes give, it is true, the sensation 
of relief, but they cannot properly be called stereoscopic. W hat 
gives the notion of relief is that our two eyes do not see exactly the 
same image of an object ; it is this princijde which has been utilized 
in the stereoscope, in which a different ima.:e of an object is placed 
before each eye so as to produce a single impression. In the bino- 
cular microscope, on the contrary, there are not two different images ; 
it is the same image wFich is presented to each of the eyes of the 
observer. The sensation of relief is the result of an illusion founded 
on habit, and consequently this kind of microscope cannot be con- 
sidered stereoscopic. Moreover, these instruments have the incon- 
venience of diminishing the clearness of the image, and it is not 
possible to use them with the higher objectives. The only way of 
obtaining with the microscope a notion of the relief of objects and 
of their suj)erposition is by employing the ordinary microscope with 
objectives of large angle of aperture. As these only allow extremely 
limited portions of the objects to be seen, we get a complete know- 
ledge of the latter by varying the focus by means of the fine adjust- 
ment. The respective situations of two points of the same object 
and of two different objects will be determined by the impression 
conveyed by the alteration of the fine adjustment necessary to see 
them successively. In short, the binocular or stereoscopic microscope, 
which is a good instrument for demonstration, cannot be employed 
in histological researches.” 
The views held by microscopists in this country are, it is needless 
to say, widely different from the foregoing, and agree with those ex- 
pressed by Dr. Carpenter in ‘ The Microscope and its Eevelations.’ 
