196 THE AMEKICAN MONTHLY [Nov 



000th of the 1-360, 000th the amount of light coming 

 from the corresponding part of the object. 



If I use a one-twelfth in the first microscope and a 

 sixth in the second, the magnification will be 2,000 

 times 600 diameters or 1,200,000 diameters which equals 

 an area of 1,440,000,000,000 times that of the original 

 object. This seems incredible, but I have already ob- 

 tained evidence of being able to pliotooraph a magnifi- 

 cation of over three million diameters, or over twelve 

 trillions of times the area. But if I mistake not, the 

 limit is far beyond this, and that limit is one of photo- 

 chemistry and not of photography as hitherto known. 

 Beyond a certain point the rays will doubtless grow too 

 weak to effect chemical changes. The energy may not be . 

 sufficient to decompose the molecule, no matter how long 

 the ray acts. We do not know where that limit is, but 

 it can be shown to be very far beyond three and a half 

 million diameters. 



If in addition to using the larger lenses of the double 

 microscope and to the exclusion of dust and aqueous vapor, 

 we also put the entire apparatus inside of an actinic- 

 proof box, Ave still farther extend this capacity to act with 

 a fainter light. If only one-tenth less light can be used 

 it will make possible ten-million diameters or one hun- 

 dred trillion areas. If one-hundredth the amount of light 

 can be used, then 100,000,000 diameters are possible. So 

 far, I am quite sure of being able to effect more than 

 3,500,000 diameters ; how much more we do not now know 

 and that is what I am busy upon. 



There is another source of leakage and interference 

 that has not, so far as I know, been hitherto corrected, 

 namely, that which occurs in and between the objective 

 and the condenser. Light from all directions impinges 

 upon the condenser, upon the glass-slide, upon the tissue 

 being examined, upon the cover-glass, and upon the front 

 surface of the objective, thus distorting and weakening 



