264 MEMORANDA. 
tion to the subject of manufacturing a portable article on the 
French principle, but with care as to optical details. He, in 
reply, stated that a small pocket lens of the kind referred to 
could be manufactured, upon the working of which reliance 
might be placed, and which would answer every purpose 
required by a microscopist in search for diatomacez, desmidez, 
or infusoria, but that the price could not be less than five 
shillings. 
As a proof of the power and clearness of the better Stan- 
hoscopes of French manufacture, I may state that I can 
recognise with ease Nitzschia closterium, N. reversa, and even 
Cocconeis excentrica, when they have been prepared and the 
endochrome has been removed by acid.—T. P. Barxas, New- 
castle-on-Tyne. 
On the Improvement of the Compound Microscope.—You 
would much oblige me by the insertion of the following 
remarks on the improvement of the Compound Microscope, 
as sequel to a contribution of July, 1863, to which I must 
refer your readers. Concave mirrors in place of lenses in the 
eye-piece, so inclined as to reflect the body of rays into the 
form of a figure of 4, would afford a convenience of manipula- 
tion almost irrespective of the dimensions of the instrument. 
If approved, a mirror as objective also might afford additional 
mechanical facilities. On a smaller scale the form of the 
letter N might be preferred. Attached to each objective 
should be a length of tube twice or more its focal distance. 
To avoid moving the body of the instrument, I would apply 
the adjustments to the stage. 
The experimental instrument of glasses described in 1863 
performs admirably, on a white enamelled watch-case, on the 
surface of a flea, on solid deal, on mouse’s hair, and on the 
surface of the pollens of whin, broom, and geranium, without 
condenser. The field is remarkably flat, and available at 
every part.—F rep. Curtis, 44, Church Street, Stoke Newing- 
ton, N 
The Rev. M. J. Berkeley and Mr. Hogg.—In the January 
number of the Journal, p. 21, Mr. Jabez Hogg has brought 
a charge of inconsistency against me which is quite un- 
founded. 
In the first place, the passage in the ‘ Outlines’ cited by him 
does not run “it is possible,” but “it is probable.” And, in 
