144 



two sections of a pill box. The t\\'0 

 halves of a diatom covering are fastened 

 together with a sort of elastic belt that 

 allows the plant to grow during its 

 lifetime. 



Tlie shell covering is so thin and 

 strong that the diatom can float about 

 in water. Since this glassy covering will 

 not permit any water to seep through 

 to the plant growing inside, the box- 

 like shell is pierced by minute pores 

 that enable the diatom to absorb both 

 food and water. The diatom stores up 

 its food— not as starch or sugar, as other 

 plants do, but in the form of drops of 

 oil. Numerous scientists have come to 

 the conclusion that we owe many of 

 our petroleum deposits to the industry 

 of the hard-working diatoms. 



The shells that encase the diatoms 

 are ridged and molded in an infinite 

 variety of ways, giving strength to the 

 structure. The designs of the trans- 

 parent structures are so beautiful, when 

 seen under a microscope, that enthusi- 

 astic diatom students have called these 

 forms of life "Jewels of the Vegetable 

 Kingdom." Experts have classified 

 more than 10,000 different varieties of 

 diatoms— each individual variety differ- 

 ing from all others in size, shape, and 

 shell design. 



When a diatom dies, its shell— 

 which is practically indestructible- 

 drops to the bottom of the body of 

 water wherein the plant has spent its 

 hfe. It joins the countless billions of 

 diatom shells already there. In time, 

 this process builds up a considerable 

 deposit of the tinv shells. The deposits 

 of diatoms, called diatomaceous ^ilica 

 or earth, as it is mined today, are one 

 of man's heritages from the Miocene 

 age. Nature was occupied for many 

 millions of years in accumulating the 

 deposits. 



The numerous lakes formed during 

 the Miocene age, as well as the sea 

 waters of that time, appear to have con- 



LOWER PLANTS, DISEASES, AND MEDICINE 



tained a greater-than-normal amount of 

 silica in solution, probably as a result 

 of volcanic activity. So it was that the 

 diatoms flourished and multiplied as 

 never before, or since. To this condi- 

 tion, then, we owe the vast deposits of 

 diatomaceous earth that we have today. 

 All except minute traces of other sub- 

 stances have disappeared, and the 

 present material is practically pure 

 silica, shapeless in nature rather than 

 crystalline. 



Today men take "white gold" from 

 the diatomaceous deposits. In Nevada 

 there is an entire mountain of di- 

 atomaceous earth, locally known as 

 "Toothpowder Mountain." Many mil- 

 lion pounds of the material have been 

 removed, with little apparent decrease 

 in the bulk of the mountain. Another 

 deposit in California occupies an area 

 of five square miles and extends down- 

 wards for more than fourteen hundred 

 feet. 



The crude diatomaceous earth is re- 

 moved from the deposits by quarr)'ing, 

 or, as it is frequently termed, "open pit 

 mining." Var)'ing thicknesses of "over- 

 burden," of course, must first be re- 

 moved in order to reach the pure ma- 

 terial. 



Much of the diatomaceous earth 

 used today is quarried with power 

 shovels. Since the uses of the material 

 depend a great deal on the preservation 

 of its original structure, however, hand 

 quarr}'ing is also used where extra care- 

 ful handling and selection of material 

 are required. 



Little commercial use was made of 

 this shell-earth until 1870. Then it was 

 that Alfred Nobel, of Nobel Prize 

 fame, made dynamite by soaking sticks 

 of diatomaceous earth in nitro-glvcer- 

 ine. Tliis one invention would have 

 been enough to make diatoms famous, 

 because dynamite has been responsible 

 for much of the large scale mining, rail- 

 road construction, and building in our 



