138 Sir George Shuckburgh Evelyn’s Endeavours 
go inches, which is now the property of the Royal Society, is 
kept in their archives, and is said to have been used by Mr. 
Bird, in dividing his large mural quadrants.* Besides these, he 
made two standards of three feet, by order of the House of 
Commons, of which I shall speak more hereafter. The mode 
of using this instrument is as follows. 
(§. 8.) Let the object to be measured be supposed to be 
about six inches, and let it be desired to compare it with the 
interval between the 20th and the 26th division on the scale c d: 
move by hand the microscope h , with its sliding plate, until the 
division of the index at k coincide with the division of 20 inches 
on the rule jfg ; then move by hand also the microscope i, with 
its sliding plate and appendage l m n 0, until the index division 
near m coincide with 2 6 inches on fg: the axes of the micro- 
scopes, or centres of their cross wires, will be at the approximate 
distance of 6 inches. To correct this, examine if the wires of 
h correspond with a division on c d ; if not, move the rule f g 
backward or forward, by the screw g , till they do, then will 
the microscope b be adjusted. Now examine if the wires in i 
cover exactly a division ; if they do so, the true interval of 6 
inches between the microscopes is obtained; if not, move 
the microscope i a little, by means of the screw /, till they do, 
dnd both the microscopes will be adjusted : then remove the 
rule c e d from its place, by taking out the screws ced, and 
place the object to be measured in its room, at the same time 
taking care that it be exactly in the focus of the object glass of 
the microscope, in such manner that one extremity may cor- 
respond with the wires in the microscope b; that done, if the 
other extremity coincide with the wires in i, the dimension 
of the object is exactly 6 inches ; if not, restore the coincidence* 
* A farther account of these scales is given in the Appendix, 
