THE GREAT STAR MAP 437 



can be made very accurate, though there are some difficulties, 

 especially those resulting from gradual wear in the screw- 

 when it is used thousands of times. But though accurate, it 

 is very slow. It is far quicker to abolish the screw and 

 substitute a finely divided scale in the field of view of the 

 microscope. It has been shown that the fractions can in this 

 way be read off at sight without losing time in turning a 

 screw. The rapidity of the process naturally excited the sus- 

 picion at first that it might be too rough ; in order to combat 

 this prejudice, one of the advocates of the new method took 

 over his apparatus to Paris on the occasion of the assembly 

 of 1896 and offered to give a demonstration. A committee 

 was appointed to sit upon him: they shut him in a room with 

 his machine and a plate he had never seen before ; he was to 

 produce as many measures as he could in half an hour. At 

 the precise second completing the thirty minutes the door was 

 opened and his measures impounded. It was found that the 

 prisoner had measured twenty-five stars with satisfactory 

 accuracy, and by many this demonstration of the qualities of 

 the machine was accepted as sufficient. With experience a 

 still greater pace can be acquired but we may take fifty stars 

 per hour as a fair average rate for one person (though two 

 people working together can do better). Now it is easy to 

 spend two or three hours on the same fifty stars if we use 

 a screw instead of a scale, so that here again we have a 

 danger of unduly prolonging the work. 



The view here expressed that it is stringently necessary 

 to study economy of time and labour is frankly that of 

 an advocate. On the other side there is considerable weight 

 of tradition and opinion which remains unshaken even by 

 such consequences as the great delay in completing what 

 was originally intended to take ten years. Our scientific 

 traditions have come down to us from times when workers 

 were so few and scattered that almost anything they produced, 

 however planned, was precious if not priceless ; we see the 

 consequences of this early practice in some huge editions of 

 the correspondence of great scientific workers in which nothing 

 is too commonplace to be included. It is quite possible that 

 considerations of economy have been rightly disregarded in 

 dealing with this sacred past ; but does this justify a similar 

 attitude with regard to the future which is better under our 



