THE MICROSCOPE. 351 



is produced behind the object-glass a magnified inverted image, which 

 received on a white surface from twenty to thirty feet distant, may be 

 seen at once by any desired number of persons. 



The sharpness and clearness of the images of a solar microscope, 

 still more (on account of the less intensity of the light) of a gas-micros- 

 cope, fall far short of those of the compound miscroscope. There are 

 incomputably fewer of the details of an observed object to be perceived 

 with the best solar microscope, with like magnifying qualities, than 

 with an indifferent compound microscope. It were a great error to 

 believe that, in reference to the practical adaptation of a microscope, 

 we should take as a measure the greatest enlargement which it is ca- 

 pable of effecting. Incomparably more important is it that the micros- 

 cope should exhibit the outlines of the observed object with the utmost 

 possible sharpness, and the component details in the greatest possible 

 number. Both requisites will be the better fulfilled, the more com- 

 pletely the spherical and chromatic aberration are averted through 

 the adjustment of the cooperative lenses. In lenses for solar micros- 

 copes no optical artist has thus far succeeded in attaining the degree 

 of excellence possessed by the optical part of the compound micros- 

 cope. We shall presently return to the working capacity of the 

 microscope as independent in certain respects of its magnifying power, 

 and illustrate it by some examples. In the mean time let these sug- 

 gestions suffice to show the value of the showman's statements, in 

 cases where they conflict with the judgment of the scientific investi- 

 gator. It should not, however, in dismissing this subject, be said, that 

 among these itinerants there are not to be found qualified individuals, 

 to w r hom, next to their gains, the instruction of the gazing public is 

 not indifferent. But only two many charlatanisms of the worst kind 

 are practiced. We remember an instance where the circulation of the 

 blood in human hair was exhibited to the believing spectators and 

 hearers ; another, where the showman pointed out the movable thorn- 

 shaped excrescence on the back of the common wheel animal, as its 

 heart, which this remarkable creature carries about with it on a stake. 

 And not one of these exhibitors of sun and gas microscopes, whom 

 we have had an opportunity of seeing, but has presented to the crowd, 

 as infusoria existing in every drop of water, the larva? of gnats and 

 even dragon flies — animals several lines in length, of which not only 

 the outline but the separate parts are visible to the naked eye, and 

 which only exist in standing water, rich in many other organisms ; 

 in water which swine, at all particular, would not drink. The spas- 

 modic contortions of the death struggle of animals in the exhausted 

 water were set forth as an example of the war of all against all, and 

 if one glanced by another, that signified that it had devoured it. But 

 let the drinkers of water take courage: We here record for their 

 comfort, that in water which appears crystal clear to the naked eye, 

 not even the microscope has been able to detect any sort of animal. 



Microscopic vision differs chiefly from that with the naked eye, in 

 that the instrument, in a great degree, refuses accommodation to the 

 organs of sight with reference to distance. We see clearly through 

 the microscope only the parts of the object lying in a determined hori- 



