i877-J 
Physics. 
I 39 
satellites ; but beyond this Mr. Todd is anxious to see the Observatory popu- 
larised as a School of Physical Science, at which regular courses of ledtures 
should be delivered on practical and physical astronomy, navigation, meteor- 
ology, magnetism, eledtricity, heat, light, and optics. 
Microscopy. — Prof. H. L. Smith, of Hobart College, Geneva, N.Y., makes 
use of the sheet wax of which artificial flowers are formed for mounting 
opaque objedts, such as the Foraminiferre, &c. Disks of suitable colour are 
punched out and pressed on a glass slide, which is warmed until the wax 
melts : when cool it will be found firmly attached to the slide, and the surface 
quite smooth and dead. A curtain-ring is pressed into the wax while warm, 
to form the cell-wall, and the whole finished off with Brunswick black outside 
in the usual manner. To attach the objedts, a minute drop of turpentine is 
applied to the wax, and before it is quite dry the objedt is placed on the 
softened wax, and when thoroughly dry it will be found so strongly attached 
that a violent blow or fall will not dislodge it. While this is being done the 
Brunswick black on the ring will have set sufficiently to fasten the cover, which 
should be of such a size as to rest, not on the top of the ring, but to slip just 
within, so that its surface will be flush with the top of the ring. When the 
cover is pressed home the whole may at once, without any danger of running 
in, be finished with the black varnish. 
A new process of histological staining has been communicated to the 
Quekett Microscopical Club, by Frances Elizabeth Hoggan, M.D. The tissues 
to be stained are membranes or soft sedtions, which may be either fresh, frozen, 
hardened in alcohol, or hardened by the picric acid and gum process ; but such 
hardening agents as the chloride of gold, or any chromate whatsoever, are 
inadmissible. The colouring agents required are — a i or 2 per cent solution 
of perchloride of iron in distilled water or alcohol (“ tincture of steel ”), and a 
solution of similar strength of pyrogallic acid in water or alcohol, the latter 
fluid being preferable in both cases. The sedtion or membrane to be stained is 
first to be treated for one or two minutes with alcohol ; the iron solution is 
filtered upon it, allowed to remain for a couple of minutes, and then poured 
off. The pyrogallic acid solution is then filtered in a similar way upon it, and 
in the course of a minute or two — the desired depth of staining having been 
obtained — the tissue is washed, and may be mounted in the usual manner, in 
glycerin, balsam, or varnish. ' The nuclei and nucleoli will be found coloured 
black, and the cell substance will also be coloured more or less, according to 
the age and other conditions of the cell. A bluish tint may be given to them 
by washing the sedtion with an alkaline water. The whole process is speedy, 
simple, and permanent. The staining may be accomplished in five minutes, 
and the materials can be bought at any country druggist’s shop. 
Dr. J. J. Woodward, of the Medical Department, United States Army, has 
made use of photography for micrometry where extreme delicacy is needed, as 
in the measurement of blood corpuscles for medico-legal cases. A glass plate 
is ruled in hundredths, thousandths, and five-thousandths of an inch : upon 
this a thin film of the blood to be examined is spread ; this is best done by 
means of the edge of a glass slide. If dried blood-stains are to be examined, 
as in criminal cases, the fragments are soaked out b}^ the usual processes. 
The photograph is taken, and the ruled lines appear with the image of the 
blood-corpuscles : the ordinary stage micrometer, covered with thin glass, 
cannot be employed, as the lines would not be in focus with the objedt. The 
measurements are made on the negative, under a magnifying glass, by means 
of a transparent scale ruled in hundredths of an inch on a thin strip of horn. 
To avoid parallax, the ruled side of the scale is placed in contadt with the 
varnished film of the negative. The process is far superior in accuracy to the 
results obtained by any form of eye-piece micrometer, and to those possessing 
the necessary photographic appliances occupies little or no more time. 
In the “ American Journal of Microscopy ” the Editor, Prof. Phin, has made 
some severe stridtures upon the statements made by Prof. P. B. Wilson, of 
Washington University, Baltimore, Md., concerning the value of infusorial 
