1874.] Physics. 417 
pencil from the obje@. Many fine glasses perform indifferently under certain 
conditions of illumination from the above cause, but, by placing a cap with a 
suitable aperture to excludg useless light, the definition is rendered perfect. 
The celebrated American }th objective, marked as having an angular aperture 
of 180°, isa remarkable instance of erroneous measurement obtained by receiving 
false light. The following are the data :—Diameter of front lens, 0'043 of an 
inch; working distance, o:013 of aninch. From these measurements, 118° is 
the utmost that can be obtained, supposing all the light entering takes part in 
the formation of the image; this glass, measured in the ordinary way, admitted 
light up to 180°. 
A series of more than eighty slides for the magic-lantern, illustrating geology 
and paleontology, have been published by Mr. James How, of Foster Lane; 
they are uniform in size with Dr. Maddox’s micro-photographs, and are photo- 
graphed from the best drawings and engravings of various fossils, sections of 
strata, and sedimentary formations. New photographs are in preparation; the 
series will prove of great value in illustrating leGtures on geological subjects. 
It is to be regretted that the colour and condition of most geological specimens 
is such as to prevent good photographs suitable for lantern magnification being 
taken directly from them. 
We have to record the death of Mr. Henry Deane, F.L.S., F.M.S., F.R.M.S., 
which took place suddenly at Dover on April rr. Mr. Deane joined the Royal 
Microscopical Society (then the Microscopical Society of London) at its com- 
mencement in 1840, and was associated with Messrs. Bowerbank, Bell, Mantell, 
Quekett, and other pioneers of microscopical science. In 1845 he discovered 
the existence of Xanthidia and Polythalamia in the grey chalk of Folkestone, 
also the now well-known Arachnoidiscus Faponica on the sea-weed used by 
the Chinese for preparing soup. He was also the first to introduce gelatinous 
mounting media, Deane’s gelatine being still employed by microscopists, 
and considered a most reliable material. It is, however, with the foundation 
and progress of the Pharmaceutical Society that Mr. Deane’s name will be 
longest remembered. He became one of the Board of Examiners in 1844, and 
introduced many imprevements of a highly practical nature into the examina- 
tions, practical dispensing being one of the most notable. He was elected 
Member of Council in 1851, Vice-President shortly afterwards, and President 
in 1853 and 1854. Mr. Deane was Chairman of the Committee appointed to 
assist the College of Physicians in compiling a new Pharmacopeeia, and also 
President of the first British Pharmaceutical Conference. Very few papers 
were written by Mr. Deane, although his work, both with the microscope and 
in chemical and pharmaceutical science, was considerable. Attention may, 
however, however, be called to “Displacement as a Method of Preparing 
Tinctures, &c.;’’* ‘ Experiments on Senna;’’{ also some on opium prepara- 
tions and extract of meat, in conjunction with Mr. H. B. Brady. 
The subject of cutting sections for the microscope has been very fully discussed 
at the Quekett Microscopical Club. A large collection of machines were 
exhibited and described by Mr. E. T. Newton. The points considered most 
needful to a perfect seGtion-cutter were a true guide-plate, and a very accurate, 
finely-divided, and tight-fitting screw; a large tube is to be preferred to one 
of small bore, and the machine should be firmly clamped to the table or bench. 
' Opinions were divided as to the form of the cutting instrument, some being in 
favour of a knife with a blade broad at the heel and narrow at the point, and 
others preferring a straight edge; all, however, ayreeing that the blade must 
be so strong that it will not bend under the necessary pressure, as in that 
case it would dip down and cut an uneven seétion, besides being liable to 
come in contact with the edges of the tube and consequently be blunted. 
It is hardly necessary to mention that success entirely depends upon the 
knife being extremely sharp. Some experienced operators consider a sharp 
knife the chief requisite, dispensing with the aid of a machine, and trusting 
entirely to steadiness of hand. Dr. Hoggan has contrived a machine differing 
* Pharm. Journ,, vol. i., p. 61. t Ibid., vol. iv., p. 61. 
