DIATOMS— CONGER 335 



nature or the reason for this wonderful quality. However, they 

 found the material useful and cut it in the form of bricks, which they 

 called most appropriately "swimming bricks." 



The earliest record we have for the commercial use of this mate- 

 rial is in A. D. 532, when the Emperor Justinian, finding it impossi- 

 ble to carry out his plans for the construction of the great dome of 

 the Church of St. Sophia in Constantinople because of the weight 

 of stone to be supported on four arches over the great expanse of 

 107 feet, resorted to the use of diatomaceous earth, or "swimming 

 brick." This was not so practical as it might seem, however, for 

 the material has little strength, and when it becomes wet, it likewise 

 becomes correspondingly heavy. 



As has been seen, the lightness in weight and the porosity of the 

 material go hand in hand. Diatomaceous earth, which weighs only 

 about one-seventh as much as water, is also sometimes so porous as 

 to be capable of absorbing as much as eight times the amount of 

 actual solid diatom substance in a given volume, or, in other words, 

 an amount of liquid equal to more than three-quarters its gross vol- 

 ume. This property has been made wide use of in a variety of 

 interesting ways. 



Wlien Alfred Nobel, founder of the famous Nobel prizes, as a 

 chemist and the inventor of dynamite, was casting about for a highly 

 absorbent material to carry the dangerous nitroglycerine in quanti- 

 ties of high potency and yet in a form that could be handled with 

 comparative safety, he turned in 1868 to diatomaceous earth. This 

 was one of the early important applications of the material. When 

 this original dynamite was used as powder in a gun, the explosive 

 force caused the extremely hard diatom shells to cut and score the 

 inside of the gun barrel. Since that time wood meal, a more expen- 

 sive, equally absorptive, but slightly more suitable material has been 

 substituted for the earth in this use. 



More lately the earth has been used for packing about the glass 

 bottles or carboys in which dangerous and corrosive liquids, such 

 as sulphuric acid, are shipped. If during transportation the con- 

 tainer should leak, or break, the acid is slowly absorbed into the 

 highly porous earth and remains as a relatively solid and dry mass, 

 arriving at its destination with no damage done. The siliceous earth 

 is unaffected by the acid, and the capillary spaces of the little shells, 

 owing to their structure, hold the acid with a tenacity which gives 

 full assurance of protection against any damage. 



Recently a Florida inventor has been developing the idea of an 

 absorbing unit to carry fuel (gasoline) for a foolproof and perfectly 

 safe kitchen range similar to, and fully as efficient as, the ordinary 

 gas stove, to be used in rural communities where illummating gas 



