64 SECOND-CLASS MICROSCOPES. 



has been or is likely to be devised, superior to this for the general 

 requirements either of the ordinary observer or of the scientific 

 student. * 



Second-Class Microscopes. 



Under this head may be ranked those instruments which com- 

 bine first-rate workmanship with simplicity in the plan of con- 

 struction ; and which may be consequently designated as ' Superior 

 Student's Microscopes.' 



45. Smith and BecFs Student's Microscope. — Of the numerous 

 patterns devised for a Monocular instrument of simple construction, 

 which shall yet be capable of answering every essential purpose 

 whether of display or of investigation, none appears to the Author 

 to be superior to that long since introduced by Messrs. Smith and 

 Beck (Fig. 35), which was employed by him for many years as his 

 own working instrument, and which he has only of late put aside 

 for the Binocular, in consequence of the advantage afforded by the 

 latter in the inquiries to which he has been specially devoting him- 

 self. This Microscope is constructed upon the Lister model, which 

 has the advantage of giving a firm support to the body along a great 

 part of its length, and great smoothness with an entire freedom 

 from twist to the rack motion ; whilst it also secures that exact 

 centering which is essential to the optical perfection of the instru- 

 ment. The upper end of the Body is furnished with a 'Draw-tube,' 

 by which its length can be increased ; and one side of this is 



* In addition to the makers above specified, the following are known 

 to the Author as furnishing Student's Miscroscopes of this class, at 

 prices ranging frora five to seven guineas, which can be recommended as 

 combining really good workmanship in their mechanical portion, with 

 an optical performance adequate to all ordinary requirements : — Messrs. 

 Baker, Collins, Highley, How, and Wheeler. The l-4th inch Objective 

 of 70° made by the last-named Optician, on the plan described in § 13 

 note, for his five-guinea Student's Microscope, may be specially men- 

 tioned as bringing out the markings of the Podura-scale with a force 

 and clearness that show this objective to be eminently adapted for 

 Physiological purposes, although it can scarcely resolve the easiest of 

 the Diatom-tests (see § 137). — For a long time after the Microscope had 

 been brought to high perfection in this country, those who desired cheap 

 and simple instruments could only obtain them from Continental 

 opticians ; and the Microscopes of Chevalier, Nachet, and Oberhauser 

 were formerly introduced very largely into this country from Paris, a 

 few also finding their way hither from Germany, amongst which those 

 of Kellner (of Wetzlar) were specially distinguished for their excellence. 

 The low-priced models of these makers, however, were all of them 

 originally vertical ; and it has only been within a comparatively recent 

 period that the power of inclination has been given to them, chiefly for 

 the British market. The great increase in the demand for Student's 

 Microscopes, which has been created in this country by improvements in 

 Medical Education, has called forth (as has been shown) a corresponding 

 supply ; and it may safely be said that the best instruments of the Third 

 Class now constructed in London can compare so favourably both in price 

 and convenience with those of Continental make, that little or nothing 

 can be gained by having recourse to the latter. 



