14 



DESICCATION 



periments ; the air is composed of two different fluids, the one of which attracts not 

 the phlogiston, and the other has the quality of attracting it.' Scheele : Experiments 

 on Air and Fire. 



DEPILATORIES. Preparations for removing hair from the skin. These are 

 said to have been much used by the ancients. In modern times they have boon used 

 as cosmetics to remove superfluous hair from the face. Lime and the tersulphuret of 

 arsenic (orpiment) are the constituents of most of the ancient and modern depilatories ; 

 but the use of orpiment is dangerous, especially if there is any abrasion of the skiu. 



The best and safest depilatory is said, in Gray's ' .Supplement to the Pharmacopoeia/ 

 edited by Kcdwood, to boa strong solution of sulphuret (sulphide) of barium made into 

 a paste with powdered starch. It should be applied to the hair immediately after it 

 is mixed, and allowed to remain there for five or ten minutes. 



DEPOSITION- OP METAI.S. See ELECTRO-METALLURGY. 



DERBYSHIRE SPAR. Fluor-spar, or fluoride of calcium. See FLUOB-SPAR, 



DERltXATIlff. A variety of serpentine found in reniform masses, in thin coat- 

 ings on the serpentine of Waldheim in Saxony. 



DERRICK CRANE. The term Derrick is applied to a temporary crane, con- 

 sisting of a spar supported by stays and guys, carrying a purchase for loading or un- 

 loading goods on shipboard. The Derrick crane is somewhat similar in its plan, the 

 projecting iron beam, or derrick, of which, can be raised or lowered to any desired 

 angle. 



DESCXiOIZXTE. A South American vanadate of lead, named after the French 

 crystallographer Des Cloiseaux. 



DESICC ATION. The act of drying. 



Davison and Symington patented a process for drying or seasoning timber, by 

 currents of heated air. Even after wood has been dried in the ordinary manner, it 

 contains much moisture, which it is still necessary to remove. The patentees have 

 given some curious results of this desiccating process : 



Temperature of air 214. 



White wood, lime tree. 



1 It will be observed, on referring to tho last column of lime, that the wood, althongh kept in the 

 chamber exposed to heated currents for 60 hours, weighed nothing less after the first 34 hours. 

 ( WJiishaw.) One application of the desiccating process for timber is to expose it for some hours to 

 the heated currents of air, and then, in its heated state, immersing it suddenly in any of tho 

 approved antiseptics, creosote or coal-tar. The result is, that the air-vessels of the wood, If not 

 entirely empty, contain air at so very high a temperature that a vacuum is instantly formed, and 

 every pore is immediately charged with the cold antiseptic in which the wood is immersed. 



