392 Prof. G. Forbes. Exterior Ballistics. [Dec. 19, 



The human brain shows signs of having expanded more decisively 

 in some parts than in others, yet that expansion, if we except the 

 visual and olfactory areas, has been general in kind. 



By super-imposing on our cerebral plans drawn from naked-eye 

 inspection others giving the results of histological examination, this 

 as a preliminary to the final localisation of function by the physiologist 

 and workers in other departments, all existing doubt on various 

 homologies may be removed. 



" Exterior Ballistics. ' Error of the Day,' and other Corrections to 

 Naval Kange-tables." By Professor GEOKGE EORBES, E.R.S. 

 Received December 19, 1904, Eead January 26, 1905. 



One of the most common problems that meet artillerists is that of 

 correcting for retardation caused by air-resistance, this being propor- 

 tional to the air-density. The published range-tables, as calculated for 

 any type of gun with given weight and form of shot, and given 

 charge of powder, are based on trials with different elevations when 

 the range and time of flight are measured directly. The range-tables 

 are calculated from the experiments by making corrections for muzzle 

 velocity and for air density. The problem now before us is to find a 

 simple rule for deducing from the published range-table another 

 range-table with a different air-density. 



Abscissae represent ranges. 



Ordinates represent elevations. 



PP' range table elevations at normal air density. 



QQ' with air density increased 10 per cent. 



QP = T ' T OP, Q'P' = T \ OP 7 . 



The solution of this problem, for flat trajectories at least, is 

 extremely neat when stated geometrically. Draw a curve in which 

 abscissae are ranges and ordinates are the elevations of the range-table. 



