42 HOW TO USE THE MICROSCOPE 



geologist makes much use of this dehglitful and 

 valuable accessory. For the best and most highly 

 finished polarizing apparatus a good deal of money 

 can be paid, but the ordinary worker will find the 

 less expensive forms quite satisfactory. Messrs. 

 Watson supply complete apparatus, with a selenite 

 film, for 17s. 6d., while Messrs. Williams and Co., 

 the makers of the "Wonder" microscope, list 

 quite a good polarizing outfit for 15s. 



The earnest worker naturally wishes to preserve 

 records of his observations, not only in the way of 

 written notes, but also by means of drawings. A 

 person possessing drawing accomplishments may 

 feel able to draw objects without assistance, but 

 all microscopists are not good draughtsmen, and 

 the majority are glad to avail themselves of some 

 form of Camera Lucida — a device whereby images 

 of objects are apparently projected on to paper so 

 that they may be fairly easily outhned with a pencil. 



The least expensive form of drawing apparatus 

 is Beale's Neutral Tint Camera, consisting of a thin 

 plate of neutral tint glass mounted at an angle of 

 45 degrees. It costs 5s. or 6s. The brass tube to 

 which the glass is fixed is shpped on to the eye-piece, 

 or body tube, after the eye-piece cap has been 

 removed. The microscope is inchned horizontally, 

 and raised on a box or book so that the central axis 

 of the tube is distant 10 inches from the table. The 

 drawing paper is placed flat on the table below the 

 eye-piece. The observer's eye is directed on to the 

 neutral glass, which reflects the image of the object 

 upwards. But although the image is really reflected 

 to the eye, it appears to be thrown on to the paper. 



