360 



Astronomical and Nautical Collections. 



different lines are therefore laid down from three different loga- 

 rithmic scales, such that the distance from 1 to 2 on the line B is 



to the distance from 1 to 2 on the lines L and C, as 2 ° 3 to L the 



350 



similar distance on the line H being only as great ; the sum 



150 & 



of these distances on the lines B and H amounting to • so that 



& 150 



if B and H were equal, this sum would represent their square, as 



it obviously ought to do, while in other cases it would approach 



very near to the square of a mean diameter equal to H + __ 



(B - H). 



The same result might also be obtained from a table constructed 

 according to this formula as from the rule, adding together the 

 logarithm of B, H, and L, that of 294 being previously subtracted 

 throughout from the numbers of one of the former columns, so that 

 the third might serve both for L and for C. 



