Dr. Goring on Microscopes. 209 
way of using very deep ones without destroying their eyes*. [ 
humbly recommend the contents of this paper to opticians, without 
being at all ambitious to acquire the honour of teaching them 
their own profession. I have the highest consideration for their 
practical knowledge, and conceive that one ounce of it is worth a 
ton weight of that of a mere theorist; at the same time I hope 
they will accept of my apologies for pointing out a few circum- 
stances to them, (certainly not of much importance,) which the 
value of their time and the multiplicity of avocations of higher con~ 
sequence will not usually permit them to attend to. If what I 
have written shall prove of no service to them, itis quite clear that 
my labours have been utterly useless. Indeed, it is too much the 
case that the researches of amateurs only terminate in discovering 
something which was perfectly well known before, and which only 
therefore serves to shew their own shallow acquaintance with the 
subject, or in bringing forward something as an improvement 
which has been tried and rejected long ago by those practically 
versed in the mysteries of optics. 
Art. IV.—Hints on the possibility of changing the Residence 
of certain Fishes from salt water to freshu—By I. Mac 
Cuxttocn, M.D., F.R.8., &c. 
Iy the tenth volume of Tilloch’s Journal, there is a paper on the 
means to be employed for multiplying fish, translated from one 
which appeared in the Monzteur, by Monsieur Nouel, of Rouen. 
Although the chief speculations of this writer, which are of a very 
* They may, perhaps, also thank me for informing them that Mr. Cornelius 
Varley, of Upper Thornhaugh-street, Bedford-square, (the inventor of the 
graphic telescope,) worked the small lenses for me which I have described ; 
they were polished on wax tools, the figure is as correct as that of any shallow 
lenses, and their image will bear magnifying perfectly well. Mr. Varley and 
“Mr. William Tulley of Islington, are the only individuals I know who can 
make such deep lenses as they ought to be made. 
