70 



PHOTOMICROGRAPHY 



(ii) The Fine Adjustment should be of exceptional workmanship. There are 

 some microscopes sold where it is not worthy of the name. 



Several forms exist and opinion very much varies which is the best. Dr. Dallinger, 

 w^ho is such a veteran microscopist, expresses his belief (see latest edition of Carpenter 

 on the Microscope), that the ideal form is that adopted by the eminent firm of Powell 

 and Lealand, Fig. 29, and that, although designed over forty years ago, has never 

 been beaten and rarely if ever equalled. On the other hand many, whilst admitting 

 the excellence of all work coming from the workshops of so celebrated a firm, prefer 

 the model as made by Messrs. Watson & Sons, shown in Figs. 32, 33, 34 and 37 ; 

 whilst Mr. Nelson — and to mention his name immediately engages the attention of 

 any one professing to know or evfen to have heard anything about the microscope — in 

 the model called after his name, and sold by Baker of Holborn, selected that particular 

 design known as Campbell's Difierential Screw. It is illustrated in Fig. 38, but for a 

 detailed description we must refer the reader to works on the microscope. 



Others strike out a difterent path and prefer the complete Continental pattern, a 

 type of which is seen in the fine adjustment met with in the Zeiss lA Stand, Figs. 35 

 and 36. 



Selection of the microscope then is a personal matter, and it appears to us not to 

 matter much, provided whatever is chosen be really of fine manufacture. In our case 

 we are very content with the Continental design as made by Zeiss in his lA stand, 

 which we are constantly using, and were it not that the lubricant used by the firm 

 requires modification, no reasonable microscopist could want anything better.* The 

 drying up, or otherwise spoiling, of the lubricant, however, is a most annoying 

 matter ; for example, just as an object is being finally focussed before taking a photo- 

 graph, to find the fine adjustment ivont work ! On these grounds we venture, for the 

 benefit of our readers who employ this firm's otherwise excellent stand, to append a 

 footnote showing how to clean and rectify the adjustment when it becomes 

 clogged, t 



* The author does not say this without justification. He used this stand to take all the photographs in this book 

 and also those in '' An Atlas of Bacteriology,"' of which with Dr. Slater he is joint author. 



f On the stem of the microscope, underneath the milled head of the fine adjustment, after lowering by its means the 

 microscope towards the specimen, will he seen on each side a small hole. A piece of soft steel exactly the size to fit these 

 holes must be procured about 2 inches in length. Placing the pin in the hole, it is turned in the opposite direction to the 

 hands of a watch ; round and round, until the top comes off. Looking inside, a key screw will then be seen, which has to 

 be undone by inserting a key properly made to fit. A few turns in the same direction as the first screw and it is released 

 and with it the spring. The body will then come otf, and can be cleaned by passing through it a handkerchief several 

 times. No lubricant I know of equals fine chronometer oil put on very thinly — tallow and wax, so often used, are 

 abominable, and turn green after but a short interval of use. Both the keys can be procured to fit at a trifling cost from 

 Mr. Mason, optician. Park Eoad, Clapham. 



