Dr. Goring on Microscopes. 209 



way of using very deep ones without destroying their eyes*. I 

 humbly recommend the contents of tods 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, it is 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 tie possibility of changing the Residence 

 of certain Fishes from salt water to fresh. By I. MAC 

 CULLOCH. M. D., F. R. S., &c. 



IN 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 Moniteur, 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 ot 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. 



