334 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



The whole bulk would be very light in weight, and would really con- 

 sist of very little actual substance, and the interspaces between and 

 within the boxes, representing porosity, would be a very considerable 

 part of the whole volume. If, further, these little cardboard boxes 

 were perforated with countless pores, they would offer a still greater 

 amount of surface and still less actual material, and in this respect 

 they would still more nearly resemble the diatom shells in a mass of 

 diatomaceous earth. 



We can get the best conception of the qualities of diatomaceous 

 earth upon which its value rests, if we think of it in terms such as 

 these: The delicate shells of the diatoms which compose the earth 

 represent surface and area, with relatively great quantities of en- 

 closed space; whereas sand or other solid particles of silica, the 

 same substance, represent volume or mass, and consequently much 

 greater weight in proportion, and much less surface area and pore 

 space (pi. 9). Consequently, the latter particles fall rapidly through 

 air or water because they are heavy; also they have less surface for 

 the absorption of heat, and less pore space for the absorption of 

 fluid. 



In fact there is no other substance which can take the place of 

 diatomaceous earth for many of the uses to which it is put, and 

 there is no other organism or process capable of producing such a 

 substance. In other words, it cannot be duplicated; the prediction 

 may even be warranted that this is one substance man will never 

 be able to produce synthetically or even find a suitable substitute 

 for. Please bear in mind again that it is the size and structure 

 alone which give it these unusual qualities, and of these it is the 

 structure only which man cannot reproduce or imitate and which 

 is produced by no other organism, nor found in any other natural 

 material. Human ingenuity has been able to spin threads as fine as 

 those of the spider, to spin such threads in as hard a material as 

 quartz, to bore almost invisible holes through diamonds, to duplicate 

 perfectly so delicate a structure as the honeycomb of the bee, and to 

 grind particles as small as, or smaller than, diatoms. Man is not 

 only able to grind such small particles, but he can make them into 

 little spheres ; but the one thing he cannot do, now, or probably ever, 

 is to make them into little hollow boxes with porous walls of glass. 

 This only the diatom can do, and in this it seems to have attained the 

 ultimate of perfection. 



Because of its porosity a block of diatomaceous earth, being much 

 lighter than water, will float on the surface of a body of water until 

 the pores fill up sufficiently for it to become waterlogged and sink. 

 This the ancients knew, though they knew nothing of the origin 

 of the material ; furthermore, they had no microscope to tell them its 



