1886.] 



MICROSCOPICAL JOURNAL. 



49 



quite necessary for high-power "work. 

 Now it is no longer so. It is prin- 

 cipally a matter of time. There is 

 nothing about artificial light inim- 

 ical to photographic action, and 

 while we admit the truth of Dr. Mil- 

 ler's criticism concerning much of the 

 amateur work with flims}' apparatus, 

 the fault, we take it, is not so much 

 due to the imperfections of the ap- 

 paratus as in the inexperience of the 

 operators. It may be confidently as- 

 serted that excellent work can be 

 done with lamp-light with powers 

 up to 1500 diameters ; but it requires 

 skill and patience, as well as a power- 

 ful light. 



We have to consider 

 now the manner of using 

 sunlight, the electric 

 light, and lamp-light. 

 In working \vith sun- 

 light it is very desirable 

 to have a heliostat. A 

 very expensive form of 

 heliostat is not necessary. 

 Mr. E.Kiibel, of Wash- 

 ington, furnishes an in- 

 strument that is in all re- 

 spects satisfactory f o r 

 this purpose, for a rea- 

 sonable price. It is rep- 

 resented in fig. 9. Full 

 instructions for setting 

 the instrument are sent 

 with each one, and there 

 is no difficulty in obtain- 

 ing a practically steady 

 beam of light after the 

 adjustments are once 

 carefully made. 



Equally good photo- 

 graphs can be made by 

 reflecting the sunlight 

 from a mirror mounted in any conven- 

 ient manner, but as the light reflected 

 upon the object is then constantly 

 changing with the position of the 

 sun, one can never be quite sure that 

 the illumination is good when the 

 plate is exposed. The few moments 

 that will elapse between focussing 

 and exposing the plate will some- 

 times make a surprising difference in 



the appearance of the object, partic- 

 ularly when a momentary cloudiness 

 causes delay in the exposure. A 

 rapid worker, however, will not lose 

 many plates from this cause, and the 

 want of means to invest in a heli- 

 ostat need not deter any person from 

 undertaking work with a common 

 mirror, which can be made to follow 

 the sun by a simple mechanism, op- 

 ei^ated inside the vyindow. 



The mirror or heliostat should be 

 mounted on a solid support outside 

 the window, or on a heavy base-board, 

 ujoon which the microscope and cam- 

 era are also fixed, thus insuringr solid- 



FiG. 9. Heliostat. 



ity to the arrangement. At the Na- 

 tional Museum the camera, having a 

 lied more than five feet in length, 

 rests upon a 3-inch plank, having a 

 guide running along one side against 

 which the side of the camera-bed 

 rests to maintain it in line. In front 

 of the camera is the microscope, 

 firmly screyyed to a block of proper 

 height, 'and at the outer end of the 



