OBJECT-FINDERS. 105 



be brought tobeai*. So, again, this sliding-plate or object-platform 



should itself be furnished with a ' stop ' for the glass slide to abut 



against, so as to secure this being always laid in the same position. 



These stops may be made removable, so as not to interfere with 



the ordinary working of the stage. Now supposing an observer 



to be examining a newly-mounted slide, containing any objects 



which he is likely to wish to find on some future occasion ; he 



first lays the slide on the object-platform, with its lower edge 



resting on the ledge, and its end abutting against the lateral 



stop, and brings the object-platform itself into its fixed place 



against the stops ; then, if, on giving motion to the slide by the 



traversing action, he meet with any particular form worthy of note, 



he reads-off its position upon the two scales, and records it in any 



convenient mode. The scale may be divided to 50ths of an inch, 



and each of these spaces may be again halved by the eye ; the 



26 

 record may perhaps be best made thus, — Tricevatium favus — 



the upper number always referring to the upper scale, which is the 

 horizontal, and the lower to the vertical. Now whenever the 

 Microscopist may wish again to bring this object under examina- 

 tion, he has merely to lay the slide in the same position on the 

 platform, to bring the platform itself into its fixed place on the 

 traversing-plate below, and then to adjust the traversing-plates 

 themselves by their respective scales.* 



77. MaltwoooVs Finder. — The 'finder' now generally used, 

 however, is that invented by Mr. Maltwood, and first described in 

 the "Transactions of the Microscopical Society, " Vol. vi. (1858), 

 p. 59. This consists of a glass slide 3 inches by 1| inch, on 

 which is photographed a scale that occupies a square inch, and is 

 divided by horizontal and vertical lines into 2,500 squares, each 

 of which contains two numbers, one marking its 'latitude' or 

 place in the vertical series, and the other its ' longitude ' or place 

 in the horizontal series. The slide, when in use, should rest upon 

 the ledge of the stage of the Microscope, and be made to abut 

 against a stop about 1| inch from the centre of the stage. — In 

 order to use this 'finder,' the Object-slide must be laid upon the 

 Stage in such a manner as to rest upon its ledge and to abut 



* This plan was suggested by Mr. Okeden in the " Quart. Micros. 

 Journal," Vol. iii. p. 166 ; and it appears to the Author that it might be 

 adopted with so little trouble or expense in every Microscope possessed 

 of a mechanical stage, that it would be very desirable for every such 

 Microscope to be furnished with these graduated scales. If the different 

 Makers could agree upon some common system of Graduation, in the 

 same way as they have adopted the " Universal Screw " for their 

 Objectives, much trouble would be saved to Observers at a distance 

 from one another, who might wish to examine each other's objects ; for 

 the numerical reference attached to each object would then enable it 

 to be found by every observer whose stage should be graduated upon 

 the same method. 



