^^2 Mcijor-Generd Roy's Account of the 



rerpe6llvely. Thus, the depth of the fides in one fenfe, and 

 the fpring which they have by bending in the other, a6b as 

 trufles, prevent the cafe from warping, and render it fuifv 

 ciently fhrong, although at the lame time, conlidering its great 

 length, very light. 



The plan of the middle rod reprefents the cafe with the top 

 off, that the tube may be feen placed therein : the right and 

 left-hand rods have the tops on, whereby may be ittw the 

 oval opening in the middle of each, fliut by a mahogany lid ; 

 and alfo the pofitions of the two therm.ometers, with tubes 

 bent at right-angles, fo as to place the ball about two inches 

 downwards within the cafe, for the better afcertaining the 

 temperature of the glafs, as will eafily be conceived, by confi- 

 dering the reprefentation of the tube and ball in the fedlioii 

 acrofs the middle of the rod. 



It is to be obferved, that the middle of the tube Is m.ade fad 

 to the middle of the cafe in the following manner. Firft, 

 around the middle of the tube, a quantity of pack-thread, im- 

 merfed in liquid glue, was wound by feveral returns on itfelf, 

 for the fpace of about two inches in length ; and upon this 

 mafs of pack-thread, while the glue was warm, a flrong ma- 

 hogany collar was forced ; whereby the three fubftances became 

 fo perfectly united to each other, that they might be confidered 

 as one only. Acrofs the bottom of the cafe in the infide, 

 three mahogany braces or girders, one in the middle, and one 

 half-way between it and each end, are faflened, by means of 

 fcrews, to the bottom and fides. Thefe rife about if inch, 

 above the bottom, fo as to place the axis of the tube, when in 

 life, about 2§ inches above the furface of the flands on which 

 it refts. The end-pieces of the cafe are likewife of mahogany, 

 about 1 1 inch thick. Each confiUs of two parts, alowerandaii 



upper.- 



