i.] ANTECEDENTS. 7 



scientific men ; probably they have been accus- 

 tomed to concentrate their attention upon a 

 few notabilities, and to ignore their colleagues. 

 It must, however, be recollected that all biogra- 

 phies, even of the greatest men, reveal numerous 

 associates and competitors whose merit and 

 influence were far greater than had been sus- 

 pected by the outside world. Great discoveries 

 have often been made simultaneously by workers 

 ignorant of each other's labours. This shows 

 that they had derived their inspiration from 

 a common but hidden' source, as no mere chance 

 would account for simultaneous discovery. In 

 illustration of this view it will suffice to mention 

 a few of the great discoveries in this generation. 

 That of photography is most intimately asso- 

 ciated with the names of Niepce, Daguerre and 

 Talbot, who were successful in 1839 along dif- 

 ferent lines of research, but Thomas Wedge- 

 wood was a photographer in 1802, though he 

 could not fix his pictures. As to the origin 

 of species, Wallace is well known to have had 

 an independent share in its discovery, side by 

 side with the far more comprehensive investiga- 



