14 Mr. J. Morrow. On the Distribution of [Oct. 27, 



in the elevation. It is gripped by the two set-screws AA, each of 

 which is screwed through one of the vertical rods C and D. Ihese 

 rods pass respectively through the pieces E and F, and are rigidly 

 attached to them. CE and DF thus form a pair of levers pivoted 

 together at JJ. Any motion of AA, therefore, will be transmitted to 

 the extreme ends of E and F. Thus if the specimen contract, AA 



Fig. 1, 



ELEVATION 



8 



5 



PLAN 



approach one another, and E will rise relatively to F; the relative 

 motion of E and F will be a measure of the contraction ot the 



SP ToTbtain the amount of this relative motion, two mirrors, M and N, 

 are used. They are made of specially prepared optically plane glass 

 The former is supported on three hard steel needle points two ot 

 which rest on F, and the third on E, as shown in the plan. The other 



