404 MANIPULATION AND PEESERVATION OF THE MICROSCOPE 



using this arrangement is seen in fig. 340. In that case, however, 

 the whole is employed for the making of a camera lucida drawing 

 with a -g^-inch objective ; it is not a desirable position for general 

 work, but was absolutely needful for the kind of investigation being 

 pursued ; and the position of the basal tripod, the microscope upon 

 it, the position of the lamp (partly seen in the immediate fore- 

 ground to the left), and the relative ease with which the entire 

 instrument is at the command of the observer, will be manifest. 

 In order to use the microscope successfully, we must have an 



illumination the inten- 

 sity of which we can 

 fully rely on. Dayliyht 

 has certain qualities thai 

 involve advantages at 

 times, and under special 

 circumstances, in its em- 

 ployment, but this is the 

 exception rather than the 

 rule. What is needed 

 is a well-made lamp with 

 a flat flame ; this we 

 should be able to control 

 with great ease as to 

 height and distance from 

 the microscope. No- 

 thing is equal practically 

 to a ^-inch or a 1-inch 

 paraffin lamp ; this gives 

 the whitest light artifi- 

 cially accessible save the 

 higher intensities of the 

 incandescent electric 

 light. But there is no- 

 thing of this kind at 

 present accessible to the 

 student. The employ- 

 ment of the edge of the 

 flame of a well-made 

 paraffin lamp used with 

 good ' oil ' has no present 

 rival. Its illuminating 

 power should be about 

 2^ candles. Gas is much yellower, and not so easy in employment. 

 To get the best form of microscopical lamp is a matter of some 

 importance. We call the attention of the reader to the best simple 

 form of lamp which will accomplish every purpose. This is a model 

 arranged by Mr. Nelson, the drawing of which is given in fig. 

 341. The lamp burns paraffin and has an ordinary J-inch wick 

 burner. The reservoir is rectangular and flat, 5J x^4 x 1J; it 

 serves three distinct purposes : 1st, it will hold sufficient oil to burn 

 for a whole day ; 2nd, permits the lamp to be lowered near the 



FIG. 341. Lamp devised by Mr. E. M. Nelson. 



