176 PHOTOGRAPHY TN ASTRONOMICAL RESEARCH. 



carefully before we can certainly accuse our photographs of a failure 

 in accuracy. Nevertheless, there are indications that we may be 

 near the limit of accuracy even now. Examination of the reseau 

 lines on various plates appears to show small displacements for 

 which no cause has yet been assigned; and the end of our tether 

 may not be far away. But as yet we have not been pulled up short, 

 and there is hope that the warning may l>e, as on one or two previous 

 occasions, a false alarm. 



Such l)eing the accuracy of the photographic method, it is sur- 

 prising that it should not as yet have been more fully adopt'ed in 

 that field of work where accuracy is of the greatest imi^ortance — 

 namely, in what is called fundamental work, with the transit 

 circle or other meridian instruments. The adoption of new methods 

 is always a slow process, and there are at least two classes of diffi- 

 culties which hinder it. The first class has it origin in the in- 

 stinctive conservatism of human nature, wherein men of science 

 differ little from theii- fellows. The second has to do with available 

 capital; and in this respect we are distinctly at a disadvantage 

 compared with other men ; for when a new^ instrument of general 

 utility is invented at once a large amount of capital is invested in 

 working out the details and improving them to the utmost, whereas 

 for a scientific instrument no such funds are available. Think, 

 for instance, of the money spent in })erfecting the bicycle, and the 

 time occupied in developing it from the earliest forms to those 

 with which we are now familiar — from the "bone shaker" of the 

 sixties through the high bicycle which we saw twenty 3^ears ago 

 to the modern nuichine. Think, too, how totally unexpected have 

 been some of the incidents in the history of this machine, such as 

 the introduction of pneumatic tires. In the case of such an instru- 

 ment, now universally adopted, if rapid development could have 

 been secured by expenditure of money and brains, surely enough 

 of both commodities were forthcoming to attain that end ; and yet 

 simplicity and finality have probably not yet been attained in a 

 period of thirty years. When we compare the small amount of 

 money and esi)ecially the small number of ])ersons that can be de- 

 voted to the pei-fection of a new scientific method, such as the use of 

 phot()gra})hy in astronomy, it will excite little surprise that progress 

 during the same j)erio(l of thirty years has been slower. In com- 

 merce old machines can be thrown on the scrap heap when improve- 

 ments suggest themselves; but who can afford to throw away an old 

 transit circle? The very fact that it has beeu in use for many years 

 rendei's its continued use in each succeeding year the wnuv ini|)()rtant 

 from consideratious of contiuuity. 



It is doubtless for such reasons as these that little has yet been done 

 in the \\ay of utilizing photography foi- uieridian observation, 



