WORKING WITH LOW POWERS. 227 



der any conditions short of sheer necessity. Now of ths 

 two styles of stands, the one with the full swing and 

 the other with the partial swing only, premising that 

 both mirrors rotate in the plane of the object, there 

 will not be a great deal of choice for general work. 

 Nevertheless it costs no more to manufacture the one 

 than the other, and hence the perfect stand becomes no 

 more costly than one that is to a certain extent imper- 

 fect. Therefore we urge, why not procure the best, 

 provided there are not especial and governing conditions 

 patent to the purchaser. The substance of all this has 

 been placed before the reader, and in again calling his 

 attention, it is hoped that the repetition will gather 

 force. 



Now all the information we have to offer as to working 

 with the low powers will refer entirely to the use of the 

 low-angled sub-stage condenser conjointly with such a 

 stand as we have recommended. As has been before 

 remarked, the introduction of the swing has worked a 

 radical change in our ideas as to the value of the con- 

 denser, and the instrument is now with us a constant 

 fixture, and in daily use. 



With the use of the condenser we have at command a 

 greater amount of light, but this is not the special advan- 

 tage derived from its use ; and then again it is easy to make 

 the bull's eye do duty in its place. Of the two accessories, 

 the bull's eye is the more simple and convenient to use; 

 nor will objects occupying the entire or greater portion 

 of the field when illuminated with the condenser appear 

 more brilliant and enticing than without it. The grand 



