PRESIDENTIAL ADDRESS. 



319 



above all things an amateur, using the word in that splendid sense to which 

 Professor Hale recently introduced us. There have been many attempts to de- 

 fine an amateur. One was given by Professor Schuster in his eloquent addresi 

 to this Section at Edinburgh in 1892 : — 



We may perhaps best define an amateur as one who learns his science as 

 he wants it and when he wants it. I should call Faraday an amateur. 



We need not quarrel with his definition and certainly not with the noble 

 instance with which he points it. But, after all, 1 prefer the definition of 

 Professor Hale s : — 



According to my view, the amateur is the man who works in astronomy 

 because he cannot help it, because he would rather do such work than any- 

 thing else in the world, and who therefore cares little for hampering tradi- 

 tions or for difficulties of any kind. 



The wholly satisfactory nature of this view is that it provides not only a 

 definition, but an ambition, and a criterion. We feel at once the ambition to 

 become amateurs, for I deny stoutly that the distinction is conferred at birth : 

 it comes with work of the right kind. And we may know what is work of the 

 right kind by this if by nothing else : that by diligently performing it we shall 

 become amateurs who find it impossible to stop : ' who work in astronomy because 

 we cannot help it.' Before an army of such men even the vast hordes of dusky 

 possibilities of which we are beginning to catch glimpses must yield. The fight 

 may seem, and no doubt is, without end; and the opportunities for glorious 

 deeds by which outlying whole troops of the enemy are demolished at once are 

 becoming rarer. We are confronted with the necessity of attacking each pos- 

 sibility singly, which threatens the stopping of the conflict through sheer weari- 

 ness. Clearly the army of amateurs is the right one for the work : weariness 

 cannot touch them : they will go on fighting automatically because ' they cannot 

 help it.' 



The following Papers and Reports were then read : — 



1. The Earth as a Radiator. By Professor W. J. Humphreys. 



Obviously, since our climates are not now perceptibly growing either colder 

 or warmer, the total amount of heat received by the earth during the course of 

 a year is substantially equal to its loss of energy through radiation during the 

 same time. But this equality of gain and loss does not apply to limited areas, 

 and therefore to map the earth as a radiator it is necessary first to obtain tem- 

 perature records above the level of vertical convection, or within the ' isothermal 

 region,' where radiation alone is the controlling factor. Now the temperature 

 of the ' isothermal region ' is known for many places, as is also the average 

 intensity of the earth's radiation, and hence it is possible to compute, with more 

 or less accuracy, the absolute intensities of the earth's radiation at different 

 latitudes. The following table is based on the assumption that the intensities 

 of earth radiation are to each other directly as the fourth powers of the corre- 

 sponding temperatures of the ' isothermal region ' : — 



Gram-calories of Earth Radiation per Square Centimetre per Minute at Different 



Latitudes. 



s Monthly Notices R.A.S., lxviii., p. 64. 



