MEMORANDA. 49 
is given in connection with the count’s letter; I therefore 
beg you will grant me this mode of addressing him.— 
T. P. Barxas, Newcastle-on-Tyne. 
[We have received a communication from Mr. Barkas, in 
which he says that since forwarding his note relative to Count 
F. Castracane’s new method of illumination he has succeeded 
in resolving the striz in Donkinia rectum, D. carinatum, and 
D. minutum, with the appliances named in his paper, but that 
the lines are exceedingly faint and difficult to detect.— 
Count F. Castracanez, “ Rome.”—Ed. Q. J. M. 8.) 
On Cleaning Glass Tubes——I have just been reading the 
communication of Mr. Wenham in the October number of 
your Journal, and certainly felt great surprise in learning the 
marvellous effects of passing a metal wire through a glass 
tube, the more so as I have for years been in the constant 
daily habit of cleaning my tubes precisely in the manner 
described without in a single instance observing the result 
mentioned. I use glass tubes with an internal diameter of 
say 1th and ;!,th of an inch. These are used to draw from the 
test-tubes the supernatant water in cleaning diatoms, and are 
afterwards most carefully cleaned by being first washed out 
and then having a pellet of cotton-wool forced through the 
bore by means of a metallic knitting-needle. This practice I 
have followed constantly for upwards of ten years, and have 
never experienced the bursting and cracking recorded by Mr. 
Wenham. I need scarcely say that the wire came in contact 
with the tube as frequently as not. Possibly the phenomenon 
mentioned in Mr. Wenham’s paper may be only produced in 
tubes of larger diameter and stouter glass. It is nevertheless 
very strange I should never have witnessed it in the small 
ones.—Geo. Norman, Hull. 
Collins’s Binocular Dissecting Microscope.—This is a cheap, 
handy, and convenient instrument. We would particularly 
allude to the great advantage of binocular vision for low 
powers in dissecting ; and to the superiority of this little in- 
strument over others at present employed, on account of its 
portability and great efficiency when in use. The case, when 
closed, measures 6 in. by 33 in. The top and front let down 
by hinges, and on them can be fitted the instruments requi- 
site for dissecting, as shown in the diagram. The sides 
draw out 5 in., and serve the purpose of rests for the hands. 
A circle of glass is in the centre of the gutta-percha trough, 
VOL. VI.—NEW SER. E 
