248 Dr. Gorin": on Chevalier's 



» 



some degree shaped to the natural curves of the spine, it is 

 made nearly straight, and projects so as to push the head for- 

 wards. A delicate girl should always sit so as to rest against 

 the back of the chair, and, if the lower part of her spine is 

 weak, a small cushion will afford great relief. As it is quite a 

 mistake to suppose that the shoulders^ if raised in any other 

 way than by the action of the muscles, or by the curvature of 

 the spine and ribs, will continue high, there is no real objection 

 to a girl who is delicate being supported by an arm-chair ; for, 

 by occasionally resting on the elbows, a considerable weight is 

 taken off from that part of the spine which is the most likely 

 to yield. 



These observations refer only to the manner in which delicate 

 girls, whose spines are still straight, should sit : when the spine 

 is actually distorted, it will be necessary to use other means. 



A Critique on the Aplanatic Object-Glasses, for diverging 

 Rays, 0/ Vincent Chevalier, aine et fils. By C. R. Goring, 

 M.D. 



The curiosity of many will doubtless be excited, as to what our 

 neighbours, the French, ever foremost in the pursuit of glory, 

 both in arts and arms, have been doing in the affair of achroma- 

 tic object-glasses for microscopes. With the highest satisfac- 

 tion I find myself enabled to state, that Messieurs Chevalier, 

 (aine et fils,) No. 69, Quai de I'Horloge, Paris, have rivalled 

 our own artists, in this branch of the manufacture of optical 

 instruments. 



Mr. J. Lister, actuated by a most laudable zeal for the pro- 

 secution and advancement of optical science, as it concerns 

 microscopes, caused me to order for him one of Messrs. Che- 

 vaher's instruments, in Mr. W, Tulley's name ; for, as Mr. L. 

 wished that Messrs. C.'s pretensions should be fairly and tho- 

 roughly scrutinized, it was but fair that the latter gentlemen 

 should be stimulated to do their utmost, by a consideration of 

 the science of their customer. A critical examination of the 

 object-glasses of this instrument (for making which every facility 

 was afforded me by Mr. L.), forms the subjectof the present paper. 



