1896.] Scientific Instruments used by the late Dr. Joule. 353 



Annals of Electricity,' vol. 11, p. 122, being reprinted to form the 

 first of the collected papers. The paper is dated January 8, 1838, so 

 that this machine must be one of the first electric motors intended 

 for practical use. 



I did not attempt to test the efficiency of the motor because the 

 wire passing round the magnet was broken in several places, and to 

 have pieced it together would have involved the unwinding and 

 re- winding of the whole of the wire on the motor. 



A New Balance ('Collected Papers,' vol. 1, pp. 552 — 561). 



A description of this instrument was read before the Manchester 

 Literary and Philosophical Society on March 20, 1886, and may be 

 found in the ' Proceedings of the Society ' (vol. 5, pp. 145 — 165). 



The balance beam is suspended by a steel wire fastened to the sides 

 of the containing box, a leaden weight is let into one end of the beam, 

 from the other end is slung a stage for the object to be weighed, and 

 for the weights ; -the centre of the box lid is cat out and roofed by 

 means of a rectangular glass box ; from the centre of the upper edge 

 of the beam there projects vertically a light wooden rod which carries 

 a small glass vessel for containing lead shot, by the addition of which 

 the stability of the beam may be decreased to any required extent ; 

 to the extremity of this rod a needle is fastened which serves as an 

 index, and oscillates in front of a graduated paper scale fixed on one 

 of the sides of the glass box referred to above. I found the balance 

 intact, with the exception that the steel wire supporting the beam 

 was broken ; this, however, was easily replaced. 



The feature of the balance is its exceeding simple and inexpensive 

 construction ; made as it is almost entirely of wood, it could be easily 

 constructed by anyone possessing a little skill in the use of tools for 

 a very trifling cost. 



The sensibility of the balance of course depends entirely upon the 

 amount of lead in the small glass bottle referred to. 



The following numbers were obtained when the sensibility had 

 been increased as far as was possible consistently with stability. 







Position of rest o 



f pointer. 



^ 









r 



A 



Mean 



Weight on stage. 



1st expt. 



2nd expt. 



3rd expt. 



difference. 



213-140 



grams 



11 



1-1 



1-3 















1-3 



213-150 



j» 



2-4 



2-3 



2-5 













1-2 



213160 



J5 



3-6 



33 



3-7 















0-55 



213-165 



JJ 



4-1 



4-1 



4-25 





