580 EHRENBERG ON THE POWER OF VISION OF THE EYE, 
100, never according to this enables us to see, with every effort, square 
objects smaller than corpuscles of 71,5 to zg'g5p of a line in 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 paca of distinguishing 
square magnitudes which are of ;z455 to zody5 of aline in diameter, 
or which amount to nearly the half of the length of a wave of light in 
the undulatory theory. With a magnifying sige of 1000 we should 
be able to discern square bodies which are of 37455 to zg4qz Of a 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 731,,5 to the g¢575 of a line, 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 ; andby 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 con amore, without 
looking to a high price; 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, which not only include the newest principles, but also 
