150 THE AMERICAN MONTHLY [Sept 



large section, for instance, for the sake of being able to 

 find it again or to tell some one else where to find it, the 

 Maltwood finder leaves little to be desired in accuracy; 

 as the object can be directly located in one of the squares 

 of l-50th inch, and by recording the position in the 

 square by tenths, readily estimated by the eye, its location 

 can be almost infallibly determined and recorded to 

 1-500 inch. But this method, though on the whole the 

 best for fine work, requires a special piece of apparatus 

 which is not incapable of being broken in careless hands, 

 and therefore falls far short of being universally appli- 

 cable. 



The rough expedient of drawing a circle on the cover - 

 glass, around the object, is also useful in some cases; 

 though much more troublesome and less precise, and 

 wholly inapplicable when many objects are to be desig- 

 nated on the same slide. 



By imagining a compass dial to be centered upon the 

 cover-glass with North at the top, the location of any 

 object can be stated ofi'-hand and instantaneously, and 

 with definitenf-ss enough for all low and medium powers. 

 Everything in the general direction from the center to 

 the top would be North (recorded as " N.") ; and by 

 beginning at the center and surveying to the to}) any 

 object tolerably easy to recognize can be promptly found 

 under any power up to frds, and with little difficulty up 

 to l-5th. In cases of special difiiculty, and often with 

 higher objectives, a medium power should be used as a 

 finder, as in other methods. By designating the distance 

 from the center by tenths (estimated) of the radius, 

 further definiteness is and should be attained with no 

 appreciable trouble. Thus an object stated to be at 

 '' N. 5 " would be half way from center to top, at " E. 9'' 

 would be at the right and near the circumference, and 

 at "N. E. 3" would be on a radius midway between the 

 two former and about one-third of the way out. Either 



