X-rays in Relation to Microscopy. By J. E. Barnard. 7 



the plate and in contact with its sensitive surface. This box 

 rotates on the centre C, the axis of which passes through the 

 plane of the object. D is a quadrant showing the degree of deflec- 

 tion from the vertical. The object therefore can be photographed 

 in any azimuth. A lead tube F is supported above the X-ray 

 tube K and is closed at each end by the lead diaphragms E and G. 

 The lithium glass window H is shown on the part of the X-ray 

 tube facing the object -box, and allows a broad beam of X-rays to 

 be emitted. 



It is of interest to compare the wave-lengths of visible light 

 with ultra-violet light, Schumann waves (the extreme ultra-violet 

 not transmitted by air) and X-rays. It will be seen that the latter 

 are of the order of one-thousandth of the wave-length of Schumann 

 waves. There is therefore a wide gap to be bridged, but it is more 

 than probable that physical research will very soon result in the 

 production of radiations of this type, in fact much has already been 

 done in this direction. The possibility of utilizing some of these 

 intermediate radiations in Microscopy must always be borne in 

 mind. 



The following are the approximate wave-lengths referred to : — 



Hertzian waves . . . 1000000 to 0*4 cm. 



Infra-red waves . . . - 13 mm. to 0'770 /x 



Visible light rays. . . 0*770 /x to 0*360 /x 



Ultra-violet rays . . . ' 360 /x to • 2 /x = 200 /x/x 



Schumann waves . . . 0*1 /x = 100 /x/x 



X-rays . . . .0*1 /x/x, about 



I am convinced that the possibility of using X-rays or some 

 allied radiation as a source of energy for microscopic work is not 

 merely a possibility, but is a problem the solution of which is a 

 reasonable certainty. It may be a long time before a definite result 

 is secured ; on the other hand the progress of physical science is so 

 rapid that at any moment a development may occur which will 

 put the whole matter on a different plane. For my own part, I 

 feel so convinced of the certainty that results will be obtained that 

 I am determined to follow the matter up with such facilities, 

 limited though they be, as are at my disposal. 



