from an Increase of Temperature. 357 



inches and a half. In order to get the wood as well seasoned as 

 possible, I selected it from the best of the oak beams got in the 

 old houses lately pulled down in forwarding the improvements of 

 Edinburgh ; and from the number of coats of size-paint which 

 covered three sides of it, there could be no doubt that it had 

 been long in an open situation. After it was worked to the pro- 

 per shape, it was allowed to stand for some weeks, as it is some- 

 times said that, to remove the surface from timber, will cause it 

 to warp, however well it may have been seasoned beforehand. 

 The stand for this instrument, however, did not alter ; and even 

 smaller pieces of the same tree, and of another tree from the 

 same place, which were accurately worked into other parts con- 

 nected with the experiments, have not altered in the least de- 

 gree. I therefore concluded that the wood had been very long 

 kept in a dry situation, To the oak stand A, which was 4j feet 

 long, all the other parts of the instrument were attached. B is a 

 double metal case containing the specimen C under experiment. 

 The bottom of the case B rests in a strong brass plate, which is 

 fixed on the top of a block of oak 8 inches broad and 11 long, 

 and the block is strongly hooped and bolted with iron to the stand. 

 The upper part of the case B is fixed to the stand by a brass clamp. 

 Fig. 2. is a cross section of the double case of the full size, and the 

 part marked ss is the space through which the current of steam 

 passes : so that the specimen C, placed within the inner case, can 

 be heated by the steam, and yet kept quite dry. P, Fig. 1, is the 

 pipe by which the steam is brought from the boiler and thrown 

 into the bottom of the double case ; and DD are eduction-pipes, 

 from the top and bottom of the case B, by which the steam is 

 carried off and thrown into the chimney, to prevent the atmo- 

 sphere of the room from being rendered damp from its escaping 

 into it. On each of the eduction-pipes DD there is a stop-cock 

 E, to regulate the quantity of steam which ought to pass off 

 from the top and bottom of the double case, in order to keep the 

 thermometers TT, which are inserted into the top and bottom 

 of the inner case, at the same height ; and by regulating the 



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