[37] For this, and some other communications upon the same subject, we are chiefly indebted to our much-lamented friend and correspondent, the late Mr. Shaw, Surgeon to the Middlesex Hospital.
[38] When the Russians wish to give a horse high action in trotting, they accustom him, while young, to wear heavy shoes on the fore feet. The resistance to be overcome necessarily increases the strength of certain muscles; and hence, when shoes of the common size are put on, the horse lifts his feet higher than one which has not been subjected to this discipline. Some opera dancers practise with lead weights on.
[39] Elderly persons may recollect how often the girls who worked at tambouring were crooked: the present fashionable amusement of embroidering seems to have, in some instances, the same effect.
[40] It must be almost unnecessary to remind the reader, that if the knees are bent in standing or walking, there is a curve in the spine at the same time.
A Critique on the Aplanatic Object-Glasses, for diverging Rays, of Vincent Chevalier, ainé 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 achromatic object-glasses for microscopes. With the highest satisfaction I find myself enabled to state, that Messieurs Chevalier, (ainé et fils,) No. 69, Quai de l’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 prosecution and advancement of optical science, as it concerns microscopes, caused me to order for him one of Messrs. Chevalier’s instruments, in Mr. W. Tulley’s name; for, as Mr. L. wished that Messrs. C.’s pretensions should be fairly and thoroughly 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 subject of the present paper. [p249]
I here, then, enter upon the discussion of the merits and demerits of the objectives of the said instrument[41], these being much more perfected than those of another, of previous make, which I saw in the possession of Mr. Howship, of Great George-street, Hanover-square, to whom I received a letter of recommendation from Mr. Spilsbury, of Ball-Haye. To the signal politeness of these gentlemen, in furthering my views, I am greatly indebted.
Four object-glasses accompany Messrs. Chevaliers’ instruments (at least those marked perfectionnés,) usually rated at the following foci: 14 French lines, 10 ditto, 4 and 4: the two latter combine together at will, and give a focus of two lines.
14.) Focus about 1.42 of an English inch, clear aperture 0.31, original aperture as reduced by a stop, 0.10.