580 EHRENBERG ON THE POWER OF VISION OF THE EVE, 



100, never according to this enables us to see, with every effort, square 

 objects smaller than corpuscles of ^^q to :fgV^ ^^ * ^'"® ^" diameter. 

 If however all circumstances are not happily combined, as is often the 

 case, it is impossible to discern even much larger magnitudes. A di- 

 stinct magnifying power of 400 allows of the possibility of distinguishing 

 square magnitudes which are of y4^riiT to ygl^oo of aline in diameter, 

 or which amount to nearly the half of the length of a wave of light in 

 the undulatoiy theory. With a magnifying power of 1000 we should 

 be able to discern square bodies which are of ^^qqq to Tja^o o ^^ ^ line, 

 and we should then distinguish Newton's elements of the red colour, or 

 be convinced that they do not exist. With a magnifying power of 

 3000, like that which Amici's microscope is said to possess, we should 

 be able to distinguish the yg Jo o *° ^^^® T^l'o^o ^^ ^ y^ne, and with this 

 must discern almost all Newton's elements of colours ; nevertheless we 

 should not yet be able to ascertain the thickness of the partition of the 

 belly of a monad, but must presume its presence only from the act of 

 the holding together of the nutritive particles. 



To pass over Amici's improvements of the microscope, which have 

 become so important, but which unfortunately are still too expensive, 

 a field has been opened to mechanism by what Selligue has made 

 public respecting compound microscopes ; and by the method of advan- 

 tageously combining several simple achromatic object glasses, already 

 applied by him to simple microscopes, and to other combinations, and 

 which has been executed by Chevalier in Paris, and by Plosl in Vienna, 

 with so much ability and success ; from which it appears that by em- 

 ploying the other auxiliary means, the power of vision of the eye may 

 be still very greatly raised by increasing the degree of magnifying 

 power which is compatible with distinctness : and the more we look for 

 a speedy improvement of optical auxiliary means from the praiseworthy 

 emulation of the distinguished, and often so completely scientific me- 

 chanists and opticians of our time, the more it behoves the observer to 

 tell his views and wants, openly and freely owning his ignorance of 

 the practical details. 



There are, as is obvious, in regard to mechanical discoveries and 

 improvements, two things especially for mechanists to keep in view. 

 On the one hand judicious treatment of the object co7i amore^ without 

 looking to a high pi'ice; and secondly, the simplifying of improvements 

 already discovered, and the greatest possible diminution of the neces- 

 sary cost by these means, in order to diffuse their application. It is 

 not indeed to be expected or desired that men who are capable of pro- 

 ducing permanent works of art should employ their time in rendering 

 their mechanism more simple ; but the incitement of others to the sim- 

 plification of their discoveries, and the multiplication of the simplest 

 constructions, v hich not only include the newest principles, but also 



