;^;^2 THE SCIENCE OF MICROSCOPY. 



And, firstly, the inicroscopist has to guard against the dis- 

 figurations of the object, and the false suggestions of its structural 

 details which may accompany excessive amplification of the image. 

 To argue that because the magnifying power of the microscope is 

 the " reason of its being '' one cannot have too much of it, is to 

 base a false inference on a half-stated fact 3 for although a certain 

 amount of amplification is the sine qua non of any visible delinea- 

 tion of a very minute object, the difficulty of good definition is 

 aggravated in every way by magnifying tJie object more and more 

 as its detail appears less distinct. The diminution of light is 

 perhaps not the worst result of this common error ; for as the area 

 of surface and depth of substance of the object pictured in the 

 microscope image (by transmitted light) diminish with the 

 increasing amplification, while the space between next-lying 

 particles or groups of elements is extended in all directions, their 

 connection with and relation to the neighbouring elements cannot 

 be kept in view except by exploring successive areas in their 

 length, breadth and thickness by successive observations, for 

 which purpose the object itself must be shifted, and the focussing 

 continuously altered. The greater the amplification the more 

 numerous must be these shif tings of scene (less being visible at 

 one time) and the more difficult to retain in mental view the 

 connection of parts. Other defects of the image-forming process 

 concur to defeat the intention of the microscopist in using excess 

 of magnifying power. The spreading out of lights and shadows 

 (crowded together in the natural object) over an area exceeding 

 that which the details in the object occupy by hundreds or 

 thousands of diameters, weakens the intensity and truth of the 

 impression conveyed. Apart from the general loss of brightness 

 the finer details are dimmed or altogether lost when pencils of 

 light of weak specific intensity lose their points, so to speak, or 

 fall short of, or beyond, the plane of the image. Again confusing 

 lights or shadows may fall in the interspaces between details which 

 are correctly delineated. These and other failures of delineation, 



