in the Chimenti Pictures, 35 



as that of a man sitting upon a stool with a pair of compasses in 

 one hand and a string in the other. He will ask what led him 

 to make a copy of it of the very same size, and without any 

 change or improvement whatever. He will ask what led him to 

 preserve such uninteresting sketches ; but, above all, he will ask, 

 with a peculiar iuterest, what led him to place these two figures 

 side by side, and in such a manner that the instant they were 

 seen by an intelligent traveller, Dr. Crum Brown, he conceived 

 that they were intended to be brought into relief by binocular 

 vision, and actually brought them into stereoscopic relief by 

 retiring and combining the two separate pictures. The histo- 

 rian of science will not be satisfied even with the obvious answer 

 to these questions. He will inquire into the date of these draw- 

 ings, and he will be struck with the fact that they were executed 

 at the time when Baptista Porta had called the attention of 

 philosophers to the subject of binocular vision, and had shown 

 in a diagram so far resembling a stereoscope slide, that external 

 objects, that is objects in relief, were seen binocularly by the com- 

 bination of a right- and left-eye picture of them. He will also con- 

 nect with these facts, though he may not yet give it much weight, 

 the statement of Professor Archer, the distinguished Director of 

 the Industrial Museum of Scotland, "that just before he left Liver- 

 pool, in a turn-out of the Museum there, what appeared to be 

 a stereoscope was found, bearing the date of 1670. Being out of 

 order," he adds, " it was laid aside at the time, and probably had 

 not been touched since. It appeared, he said, to be of Roman 

 manufacture ; and he suggested that an attempt should be made 

 to get it for examination, as having an important bearing on the 

 subject before the Society" *, namely the subject of Chimenti's 

 stereoscopic figures. 



In forming his opinion from these various considerations, the 

 historian of science will not fail to notice that the binocular 

 theory of Baptista Porta was published in Italy in 1593 ; that 

 the stereoscopic drawings which so wonderfully illustrate it were 

 also made in Italy some time after this, between 16.20 and 1640, 

 and that the probable stereoscope in Liverpool, with the date of 

 1670, is considered to be of Italian origin. 



I am, 



Ever most truly yours, 



D. Brewster. 



Allerly, November 27, 1863. 



* Photographic Journal, vol. viii. p. 12. 



D2 



