D E R 



C 72] 



D E X 



DE'RMOID. (from deppa, and tl^oQ Gr.) 

 Belonging to the skin ; resembling the 

 skin. 

 DESI'CCATE. (from desicco, Lat.) To 



dry up ; to exhaust of moisture. 

 DESI'CCATE. To grow dry ; to be freed 



of moisture. 



DESI'CCATED. Dried ; exhausted of mois- 

 ture. 



DESICCA'TION. (desiccatio, Lat.) The 

 state of being dried ; the act of making 

 dry. 

 DESI'CCATIVE. That has the quality of 



making dry. 



DE'SMINE. A mineral found in the lava of 

 extinct volcanoes accompanying spinel- 

 lane ; its form of crystallization is in 

 small silken tufts. 



DE'SPUMATE. (despumo, Lat.) To throw 

 off in froth or foam ; to discharge impu- 

 rities, or excrementitious matter in foam 

 or scum. 



DESPUMA'TION. (despumatio, Lat.) The 

 throwing off of excrementitious matter 

 and impurities in froth, foam, or scum. 

 DESQ,UAMA'TION. (desquamatio, from de 

 and squama, Lat.) The falling off of the 

 cuticle in the form of scales. 

 DE'SQUAMATE. (desquamo, Lat.) To 



scale off ; to fall off in small scales. 

 DETRI'TION. The act of wearing away. 

 DETRI'TAL. Composed of detritus ; con- 

 sisting of the disintegrated materials of 

 rocks. 



DETRI'TUS. (Lat.) The worn off, or 

 rubbed off, materials of rocks. " Beneath 

 the whole series of stratified rocks," says 

 Professor Buckland, " that appear on the 

 surface of the globe, there probably exists 

 a foundation of un stratified crystalline 

 rocks, bearing an irregular surface, from 

 the detritus of which the materials of 

 stratified rocks have in great measure 

 been derived." 



DEUTO'XIDE. > (from StvTepos and oxyd.*) 

 DEUTO'XYDE. $ A substance in the se- 

 cond degree of oxidation, or containing two 

 prime proportions of oxygen : a protoxide 

 is in the first or smallest degree ; a trit- 

 oxide denotes a third proportion, and a 

 peroxide has the greatest degree of oxida- 

 tion. 



DEVE'LOPE. (dtvelopper, Fr.) To un- 

 fold ; to disclose ; to clear from its cover- 

 ing ; to unravel. 



DEVE'LOPEMENT. (dlveloppement, Fr.) 

 In this word and that which precedes it, 

 the French derivation is incorrectly spelt, 

 in the former by Johnson, in the latter 

 by Todd, who introduces it.) The act 

 of unfolding ; the discovering of something 

 hidden. 



DE'VEX. (<7e0e.rttS,.Lat.) Inclining down- 

 wards ; declivous ; bending down- 

 wards. 



DEVE'XITY. (devexita*, Lat.) Declivity ; 

 a bending downwards. 



DKVOLTJ'TJON. (devolutio, Lat. devolution, 

 Fr. devoluzione, It.) The act of rolling 

 down, as the removal of earth or strata into 

 a valley. 



DEVO'LVE. (devolvo, Lat.) To roll down, 

 as "every headlong stream devolves its 

 winding waters to the main." In this 

 sense, however, the word is not modern- 

 ly used : in its common acceptation, 

 at the present day, it signifies to pass by 

 succession from one person to another. 



DEW. The following account of dew is 

 extracted from " Mrs. Somerville's Con- 

 nexion of the Physical Sciences:" 

 " Our sensations only measure compara- 

 tive degrees of heat : when a body, such 

 as ice, appears to be cold, it imparts 

 fewer calorific rays than it receives ; and 

 when a substance seems to be warm, for 

 example, a fire, it gives more caloric than 

 it receives. The phenomena of dew and 

 hoar-frost are owing to this inequality of 

 exchange ; the caloric radiated during 

 the night by substances on the surface of 

 the earth into a clear expanse of sky is 

 lost, and no return is made from the blue 

 vault, so that their temperature sinks be- 

 low that of the air, whence they abstract 

 a part of that caloric which holds the at- 

 mospheric humidity in solution, and a 

 deposition of dew takes place. If the 

 radiation be great, the dew is frozen and 

 becomes hoar-frost, which is the ice of 

 dew. Cloudy weather is unfavourable to 

 the formation of dew, by preventing the 

 free radiation of caloric ; and actual con- 

 tact is requisite for its deposition, since 

 it is never suspended in the air like fog. 

 Plants derive a great part of their nou- 

 rishment from this source ; and as each 

 possesses a power of radiation peculiar 

 to itself, they are capable of procuring a 

 sufficient supply for their wants." 



DEW-LA.P. The loose skin which hangs 

 down under the throat of the cow and 

 other animals, and thus called from its 

 licking or lapping the dew when grazing. 



DEX'TER. )(Lat.) The right, as op- 



DE'XTRAL. 5 posed to the left. In con- 

 chology, shells are divided into dextral 

 and sinistral. The more common turn of 

 shells is with the apparent motion of the 

 sun, or as the index or hand of a clock 

 moves. On the contrary, a reversed, or 

 sinistral, shell, when placed in a perpen- 

 dicular position has its spiral volutions in 

 an opposite direction to the motion of the 

 index of a clock, and resembles what is 

 called a sinistral, or left-handed, screw. 

 The sinistral shells are sometimes termed 

 heteroclitical, and heterostrophe shells. 

 There has been considerable confusion 

 amongst conchological writers in describ- 



