WITH THE MICROSCOPE. 15 



the aperture, just above the object. But the most beautiful effects 

 result from the use of the Lieberkuhn, 30, with direct light. 



The slide, as has been stated, is kept in contact with the lower 

 part of the instrument, which I have called the stage, by a spring 

 which is therefore made to press on the back of the slide. On the other 

 side of the stage a little screw arid clamp are placed so that the speci- 

 men may be fixed in any position that may be desired, figs. 21, 23, 

 and 27. 



In using this microscope, the slide with the object to be examined 

 is placed upon the stage, the thin glass being upwards towards the 

 object-glass, while the spring is made to press upon the under 

 surface of the slide. The little screw is removed. The slide may 

 now be moved in every position, and any particular object to be 

 examined can readily be placed exactly under the object-glass. 

 Tube a is withdrawn about two-thirds of its length. The tube c 

 being firmly held with the left hand, b is grasped with the right, 

 and with a screwing motion the object-glass is brought to its 

 proper focus. The specimen having been fixed with the little clamp, 

 and the tube fixed in its position by screwing down the ring 

 fitted on tube c, the instrument may be passed round a class. 

 This microscope seems to be well suited for field-work and especially 

 for botanical purposes. It is not heavy, and, including thepowers 

 and an animalcule cage, will easily pack into a tube or case six and 

 a-half inches long and two inches in diameter. I constantly use it in 

 clinical teaching. Various deposits, specimens of sputum, &c., may be 

 examined by the patient's bedside, and their characters demonstrated 

 to the class. The instrument is made by Messrs. Powell and Lealand, 

 by Mr. Highley, and other makers. Messrs. Murray and Heath 

 have carried out some improvements in fixing the object which have 

 been suggested by my friend Dr. Guy. 



The Stand. The arrangement of the stand will be at once under- 

 stood by reference to fig. 29, pi. VII. The structure of the lamp is 

 represented in fig. 26. It is an ordinary oil lamp with a diaphragm, 

 just level with the wick, in order to cause a powerful current of 

 air round the flame. By this means all flickering is prevented, and 

 the instrument may be moved about without fear of the light being 

 blown out. The diaphragm is made of a plate of mica, and the 

 same substance is placed over the aperture in the chimney //. The 

 lamp is made to slide in the grooves marked l>, g, fig. 29, pi. VII, and 

 it is fixed at a proper distance from the object by the screw /, fig. 26. 

 At first I used oil, but for some time past I have burnt paraffin which 

 is much cheaper and gives a far better light. When required for 

 reflected light, the lamp is placed in the groove marked g, fig. 29. A 



