43 



PLATES. 



It should g-o without saving-, perhaps, that plates giving correct color 

 values should generally be used. We have used Cramer's isochromatlc 

 mediums and Carbutt's ox'thochromatic mediums and have found them 

 satisfactory. 



CHEAP APPARATUS. 



I can think of no valid plea for cheap apparatus. Some men with 

 cheap apparatus can, to be sure, do better work than others with the 

 costliest. The difference does not lie in the apparatus; this good work is. 

 however, done at an outlay in time, patience and material that renders 

 it so costlj^ in the end as to be impracticable. This is why photomicrog- 

 i-aphy has not been more used in the past. Makers of apparatus are care- 

 ful to advertise "any microscope stand can be used." This, except for 

 low power work of the simplest character and second grade in qualitj^ 

 is a delusion. Internal reflections from the microscope tube, the objective 

 and its fastenings injure more or less everything; moreover, the trouble 

 necessary to adjust a microscope every time work is wanted is by far 

 the costliest part of the work; a special stand with a large tube fi'om 

 the walls of which reflection is impossible and into which properly con- 

 structed objectives can be screwed without a graduating series of collars, 

 mounted fii-mly on an unshakable foundation, dedicated to this one use, 

 always ready, quickly capable of adjustment for any practicable powers, 

 with a source of light that does not require long-time exposures, immedi- 

 ately adjacent to a properly equipped dark room, is not only the cheapest 

 arrangement; it is the only arrangement that will for any considerable 

 time be used by a busy man. The complete apparatus as I have described 

 it should be supplemented by a firm, permanent, upright stand for copy- 

 ing all such slides as will not permit the microscope to be brought to 

 the horizontal position. This is one exception to my general proposition 

 that cheap apparatus is too expensiA^e. The exception is, however, only 

 apparent, for this is as good an arrangement for this class of work as 

 it will admit of. This sort of camera should be at hand in every labora- 

 tory where there is any one competent to use it, for the things for which 

 it is necessary can neither be sent away nor can they await a more 

 favorable hour often. Such apparatus in convenient form has been ex- 

 hibited and described before this Academv. 



