496 



NEW INSTRUMENT FOR 



terpoise the long arm. Each division of the scale de- 

 notes the'portionof the arm which lies between it and 

 the extremity marked by the line S. G. (specific gra- 

 vity) ; and their place is found by dividing the whole 

 length of the arm from the centre to the line S. G. 

 by their numbers, so that the divison marked 4 will 

 be one-fourth from the extremity, 3 will be one- 

 third, &c. When the specific gravity of a body is 

 to be ascertained, it is to be suspended by a horse- 

 hair from the short arm, and moved along until it 

 is balanced ; the index on the slider having been 

 previously set to the line S. G. ; the body is now to 

 be immersed in water, and the equilibrium resto- 

 red by moving the slider towards the centre ; the 

 number of the division on the scale opposite to the 

 index on the slider, will be the specific gravity of 

 the body required. Supposing the index to be be- 

 twixt the third and fourth small division from 2j5, 

 the specific gravity of the body will be 2.57, each 

 small division being equal to two hundredths. 



Thus far the above instrument corresponds with 

 that already described by Dr B. H. Coates, in the 

 Journal of the Academy of Natural Sciences at 

 Philadelphia. But the scale of this instrument be- 

 comes very minute, when the specific gravity exceeds 4, 

 and almost useless in higher numbers. In addition, 

 therefore, to the scale already described, there is 

 another scale on the side of the beam, numbered 

 from 0 to 1000, and divided into 500 equal parts : 



