238 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
scopes (fig. 24) tbe focusing is also effected by a Microscope. The two 
pillars C C' carry tbe fixed bridge b in which the Microscope M is 
Fig. 24. 
0 
screwed. The objective is a dividing doublet, so that greater play has 
to be given to the movement of the eye-piece, as one or both are used, 
and for this purpose a rack and pinion a is applied. 
Boys’ Microscope Cathetometer.*— Mr. C. V. Boys, in his experi- 
ments on the elasticity of quartz fibres both to stretching and to torsion, 
devised the apparatus shown in fig. 25. 
The apparatus (made by Hilger) consists of a Microscope catheto- 
meter shown in the figure at M, which can be made to traverse a vertical 
slide by means of a fine screw having a micrometer-head, the divisions 
of which are capable of being read directly to the 1/1000 mm. To the 
end of the Microscope farthest from the eye-piece is attached the vertical 
tube T, which carries at its lower end an adjustable arm A, fitted with a 
clamp C. To the end of a separate bracket is fixed the block a, which 
supports, by means of a knife-edge, the beam B, which is weighted with 
a gravity-bob W, and carries on a second knife-edge h the micrometer- 
scale D, the opposite end of the lever being counterpoised by the 
adjustable weight P. The fibre to be tested has attached to it a pin at 
each end to facilitate its being fixed in the apparatus, it being stretched 
vertically between the scale I) and the clamp C. 
When the micrometer-head is turned, the cathetometer M is lowered, 
carrying with it the tube T, and thereby putting a tensile strain on the 
fibre, which draws down the lever B, being itself stretched under the 
* Journ. Soc. Arts., xxxvii. (1889) pp. 833-4 (1 fig.). 
