THE CAMERA OBSCURA. 277 



the life of civilised man has been quite altered, so that practi- 

 cally his sojourn upon earth has been doubled. Steam, with 

 all its various applications, electricity, and other kindred arts 

 have become so intermingled with our lives, that it is difficult 

 to imagine what our state would be if we were suddenly and 

 utterly deprived of them. The loss to all would be incal- 

 culable, ^nd not the least of the losses would be that of ready 

 communion with our fellow-creatures. 



Of these arts we will now take that which is named at the 

 head of this division of the book, and see how far it is a 

 development of natural facts. 



THE CAMERA OBSCURA AND THE EYE. 



I HAVE already spoken of arts as being akin to each other. 

 They are more than this, and every day of the world's pro- 

 gress teaches us that Art, Science, and Manufacture are sisters, 

 all born of one family, and all depending mutually on each 

 other. 



Take, for example, our present theme namely, Optics 

 and see how dependent it is upon Manufacture and Art. 

 Without the former, man could not construct those beautiful 

 telescopes, microscopes, spectroscopes, of the present day, which 

 are evidently but the precursors of instruments which will work 

 still greater marvels. 



The first enables us to see solar systems without number, to 

 which our own, vast as it seems to us, is but as a grain of sand 

 in the desert. The next instrument makes revelations as mar- 

 vellous of the infinitely minute as does the telescope of the 

 infinitely great, enabling us to see living organizations so small 

 that thirty-two millions could swim in a cubic inch of water 

 The third, a comparatively modern instrument, reveals the 

 composition of objects, and can detect and register the 

 materials of which the sun and fixed stars are made, or 

 detect an adulteration in wine. It can adapt itself equally to 

 the telescope and microscope, and the very same instrument 

 which will reveal the character of an invisible gas in the Pole- 

 star, when attached to the telescope, can, when connected with 

 the microscope, point out the presence of half a corpuscle of 

 blood where no other instrument could discover any trace of it. 



