236 SELECTION AND USE 



taken from its place. Fortunately, any drawer which is deep 

 enough, may have this device applied to it by simply glueing a 

 thin strip of wood or pasteboard on the bottom of the drawer 

 so as to raise up the part on which the slides rest, but leaving 

 a space of about three-quarters of an inch under the end of the 

 slide, into which the latter may be tipped. 



The M altwood Finder. This is a most important ac- 

 cessory to every microscope, as it not only facilitates inter- 

 change of notes between 

 microscopists living at a 

 distance from each other, 

 but it enables observers to 



MALTWOOD'S jH 

 FINDER 



make an accurate record of (< _ 

 the position of any" object, 



and thus make sure of its ri 79 



identity when under ex- 

 amination at different times. It consists of a glass slip, a lit- 

 tle wider than an ordinary slide, upon which is a photograph 

 occupying a space 1 by 1 inch, as shown in figure 79. This 

 space is divided into 2,500 squares (50 divisions on each side) 

 and each of these small squares contains two numbers, one of 

 which indicates its position from bottom to top, while the 

 other marks its position from right to left. Thus the square 

 which lies on the tenth line from the bottom, and the fifteenth 

 from the right-hand side, would be }g. 



The method of using the Finder is as follows: Placing on tho 

 stage an object mounted on an ordinary slide, with its lower 

 edge against a ledge of some kind, and its left-hand edge against 

 a stop (the stop and ledge both being movable as regards the 

 stage), we bring some particular spot into view. Removing 

 the slide, we now place the finder in its place, and read off the 

 two numbers. It is no\v evident that if at any future time we 

 should place the finder against the movable ledge and stop, and 

 bring the same numbers into view, then on removing the finder 

 and placing the slide on the stage and against the ledge and 

 stop, which, of course, must occupy the same position that 

 they did when the finder was in place, the precise spot origin- 

 allv under examination will be in view, We can therefore 



