1898] MICROSCOPICAL JOURNAL. 9 



fused light. This is why all details below a certain size 

 are lost in a photomicrograph. The space between two 

 points that are too close together on a film^is acted on 

 by the light irradiated by these points. The "two points" 

 are separated by magnification to such a distance that 

 when the photograph is made the irradiation^will not 

 cover the space between the points. 



The first microscope takes the light from a very small 

 object and spreads it over an area of sensitive plate one 

 hundred million times as great as the area of the object 

 from which it comes, hence the light has only the 

 1-100,000,000 as great an intensity as when it started 

 from the object. The light is already too weak to photo- 

 graph with if best results are desired. But select some 

 small area of this faint image and subject it to a still 

 further magnification of six hundred additional diameters. 

 This light becomes only the 1-360,000 as strong as it 

 was, and the natural eye cannot see the second magnifi- 

 cation because the light is too weak. But by remaining 

 several hours in a completely darkened room the eye can 

 see very faintly such magnification. But when a sensi- 

 tive plate, is put in place of the eye it acts cumulatively, 

 and the faint light rays which the eye cannot clearly see 

 will fall hour by hour upon the plate and slowly accumu- 

 late enough effect to make a visible picture. The struct- 

 ural lines which in the image of the first microscope are 

 too near togetlier to be photographed as distinct objects, 

 are in the image of the second microscope 600 times far- 

 ther apart and do not blend by diffusion and irradiation. 



It is not very difficult to distinguish ou a good photo- 

 micrograph, made by best modern methods, lines which 

 in the original object are not more than the one-teh- 

 thousandth of a millimeter apart, but much beyond this 

 the microscope and photo-micrography refuse to go, be- 

 cause the images of these lines on the sensitive plate 



