80 SELECTION AtfD tfSU 



of view, while Fig. 8 shows the hap-hazard way in which ex- 

 aminations are usually made, abundant room being left (as 

 shown by the small crosses) for the escape of important fea- 

 tures. Now, with ordinary clips, or even with the glass stage, 



Fig. 7. 



it is impossible to effect this, and therefore we prefer those 

 stages in which a cross-bar moves over the plate in such a way 

 that it is always parallel to the front edge of the stage. Such 

 a contrivance also affords facilities for using the Maltwood 

 finder. 



In the simpler forms of the stage, the object is held in place 

 by spring clips, which press it down, and under which it is 

 moved. These clips are frequently screwed to the stage, which 

 is a great mistake, as we are thus prevented from slipping them 

 off, and leaving the stage entirely clear. They should always 

 be held by pins, which merely slip into holes in the stage. 



The so-called glass stage has recently come into very exten- 

 sive use, and is very much liked by some. We believe it is 

 now generally conceded that it was invented by Mr. Tilghman, 

 of Philadelphia, who placed it in the hands of Mr. Zsntmayer 

 to be manufactured. In this country it is generally known as 

 the Zentmayer stage; in Europe it has been called the Nachet 

 stage. It has assumed a great variety of forms, some of them 

 radically different from the original one. Dr. Carpenter seems 

 to prefer this form of stage to all others. 



Revolving Stage. It is often desirable to rotate an 

 object in the optic axis of the microscope, either for the pur- 

 pose of measuring angles or changing the direction of the 

 illumination in regard to the object. Means for effecting this 



