Nov., 1922] SPONSLER — STRUCTURE OF STARCH GRAIN 481 
It is only a step further to break those six crystals into many smaller 
crystals, since the crystal structure cannot be destroyed by that means, 
and to pack them in a small tube of some amorphous substance, like glass 
or celluloid; to allow the beam of X-rays to pass through this tube; and 
to photograph the many minute reflections which will be produced by this 
random arrangement of tiny crystals. Since all of those small crystals 
which have their 100 planes at the proper angle of incidence to the beam 
will send their reflections out at the same angle, the sum of these small 
reflections will make a large line on the photographic plate; this will happen 
also with each of the other planes for both first- and second-order reflections; 
and as a result the photographic plate will have all six lines which might 
have been obtained by carefully manipulating a single large crystal or by 
carefully arranging six smaller crystals. 
From this it is just another step further in thought to realize that a 
powder of an unknown structure might be substituted for the known powder, 
and certain facts concerning its atomic structure be obtained from the 
photographic plate. 
Based, more or less, upon this sort of reasoning, Hull (42) and Debye 
and Scherrer (43) independently devised methods, which are very much 
alike, for studying the atomic structure of crystal powders. Since then 
several modifications have been made in the refinement of the apparatus, 
but the essential features have remained the same. They also determined 
certain conditions which must be complied with for the success of the 
method, such as the most suitable X-ray tube, and the best voltage, con- 
nected with the production of the rays; the fineness of the powder which 
will give the clearest lines, and the kind of containers for the powder. 
Through their work and that of others, means have been found for obtaining 
almost pure monochromatic beams, that is, one wave-length only; and for 
increasing the effect on the photographic film by converting the waves 
which have passed through the film into light waves. 
The experimental part of the work for this paper was done with an 
apparatus built on the principles laid down, for the greater part, by Hull 
(42, 46). 
Experimental Part 
Apparatus 
The apparatus (fig. 3) consists of two parts: an X-ray tube (its high- 
voltage electrical equipment not shown) and the photographic part. The 
X-ray tube, X, is enclosed in a lead-covered box, B. The photographic 
film, F, is placed on the circumference of a flat, semicylindrical film-holder, 
H. The powder to be investigated is pressed into a container, P, which is 
located at the intersection of all the radii from the film. The beam of 
X-rays from the anticathode. A, passes through two adjustable lead slits, 
5, S, and into the powder where a small part of the beam is reflected to 
