124 NEW BALANCE. 



plain or turned in the lathe, it can very easily be manufacj. 

 tured without requiring uncommon skill in the workman. 



3d. — As it has neither Avorking surfaces of contact, nor 

 joints nor levers, it will regularly obey the minute changes 

 of temperature, and will not act by jerks or starts. 

 Explanation 4th.— In the expansion-bar consisting of two metals, 



of the mode of connected longitudinally by soldering or otherwise, the 

 of brass and differences of length between them, when heated or cooled, 

 steel fused or are found to produce a bending of the whole bar, which 

 soldered to- jg more the thinner its component parts. Ai. the very 

 surface of contact, and at a considerable distance on each 

 side of that surface in thick bars, the principal effect must 

 consist in what workmen would call wire-drawing the one 

 metal, and upsetting the other. It is reasonable to think 

 that this process must affect the properties of a balance so 

 constructed, and cause it to deviate in the course of time 

 from its original adjustment. This objection to the com- 

 mon expansion-balance appears to be obviated in Mr. 

 Hardy's invention. The flexure of the brass takes place 

 through its whole length, in a regular manner, and is in 

 ^antity but small; and the flexure in the reduced parts of 

 the steel bar will be equally slight, if the thickness of that 

 part be made to bear the same proportion to its length. 

 Hardv'sba- Hence, and upon the whole, it may be concluded that when 

 knee has not once it is adjusted, it will not alter, and that in ail changes 

 the same faults ^^ temperature it will be similarly affected, and will return 

 to its original figure whenever the first temperature is 

 restored. 

 It is easily 5th. — Artists will probably consider it as a desirable 



™*^^* property of the present instrument, that the adjustments 



for temperature being in lines nearly parallel to the verge, 

 will have no practical effect in deranging the adjustment 

 for position. 



I have the honour to be, 

 Dear Sir, 

 Your most obedient servant, 

 WILLIAM NICHOLSON. 

 Soho-square, March 7lh, 1805. 

 To Charles Taylob. Esq. 



A cer. 



