156 



BEPORTS ON THE STATE OF SCIENCE. 



milligrammes. The weights to be used for the graduation of bulbs of 

 500 to 1,000 c.c. are given in the following table: — 



The sensitiveness of the balance and the range of movement of its 

 beam between the stops should be such as to afford a maximum range 

 of 5 per 100. By adjustment of the counterpoise the zero of the scale 

 is taken with the lever to the left of the vertical position by an amount 

 effected by a weight = 1*5 per 100 (i.e., by a weight of 30 milligrammes 

 in the case of a 525 c.c. bulb). From this zero position the positions 

 corresponding to 1, 2, and 3 per cent, are marked as the index is 

 deflected with the 5 per cent, rider at 1, 2, 3, on the left side of the 

 beam. Graduated in this way the balance is adapted to direct reading 

 up to a maximum of 3 per 100 ; the scale is relatively contracted, and 

 fine readings are not to be expected; the unit can at best be divided 

 into four quarters. This relatively insensitive form of balance can be 

 used as a recording instrument (vide infra) and corrections for variations 

 of temperature and pressure during observation are negligible. It may 

 be referred to as type A. 



Graduation by a 5 per 100 rider. — With the beam of the balance 

 divided into ten parts, the counterpoise corresponding to 1, 2, and 3 

 per cent, are most expeditiously secured by a rider of which the weight 

 corresponds to 5 per cent, of chloroform in relation to the capacity 



