ACT 



ADA 



that Mr. Miller himself is in error 

 when he speaks of the species A. 

 Moniliformis as belonging to the 

 Mountain Limestone. The generic 

 characters of the genus are thus 

 described by Mr. Miller. A crinoidal 

 animal, with a round column com- 

 posed of numerous joints, perforated 

 by a round alimentary canal. At 

 the summit of the column is placed 

 an operculum formed of three plates 

 on which five first costals and one 

 irregular costal adhere ; which are 

 succeeded by the second costals and 

 intercostals and the scapula, from 

 whence five arms proceed, forming 

 two hands, with several tentacu- 

 lated fingers. Round side arms 

 proceed at irregular distances from 

 the column which terminates at the 

 base in a fascicular bundle or root 

 of fibres. 



ACTI'NOLITE. (from aic-rlv and \lOo$, 

 Gr.) A variety of hornblende. Its 

 constituent parts are silica 46 '26, 

 magnesia 19'03, liine 13'96, alu- 

 mina 14-48, protoxide of iron 3.43, 

 protoxide of manganese 0' 36, fluoric 

 acid 1-60, water, &c. 1'04. This 

 variety of hornblende rarely occurs 

 in the secondary rocks, being princi- 

 pally confined to those of the pri- 

 mary class. It is of a green colour. 

 Cleaveland says " this mineral pos- 

 sesses all the essential characters of 

 hornblende. In fact common horn- 

 blende and actynolite insensibly 

 pass into each other. The actynolite 

 has usually a greater translucency, 

 a more lively green colour, arising 

 from the chrome which it contains, 

 and differs in the result of fusion 

 by the blowpipe. Jameson places 

 actynolite in the hornblende family 

 but, as a distinct species, divided it 

 into four subspecies, 1. asbestous 

 actynolite, 2. common actynolite, 

 3. glassy actynolite, and 4. granu- 

 lar actynolite. He remarks "Haiiy 

 is of opinion that actynolite and 

 hornblende belong to the same 

 species, because his observations 



ACTJ'LEATE 

 ED * 



shew an identity in their primitive- 

 forms. Count de Bournon, on the 

 contrary, proves that their primitive 

 forms are not the same ; hence he 

 infers that they are distinct species. 

 These two minerals are further dis- 

 tinguished by their colour, fracture, 

 and crystallizations ; those of acty- 

 nolite being few in number and 

 simple ; whereas those of horn- 

 blende are more numerous and com- 

 plex; and lastly, they differ re- 

 markably in geognostic situation." 

 Phillips places actynolite amongst 

 the varieties of hornblende, and 

 divides it into crystallized asbesti- 

 form, and glassy actynolite. 



ACTI'NOLITE-SCHIST. A metamorphic 

 rock, consisting principally of acti- 

 nolite, with an admixture of mica, 

 quartz, or felspar; its texture is 

 slaty and foliated. 



ACTINOLI'TIC. Containing actinolite; 

 of the nature of actinolite. 



(*ad**tw> Lat -) 

 Prickly; having 

 spines or prickles. 

 Applied to leaves armed with 

 prickles. Used to denote prickles, 

 fixed in the bark, in distinction 

 from thorns which grow from the 

 wood. 



ACTJ'LETJS. A prickle or spine, arising 

 from the bark only,andnot growing 

 from the wood. 



ACTJ'MINATED. (acuminatus, Lat.) 

 Ending in a point ; sharp-pointed, 

 the decrease being very gradual. 



A'DAMANT. (a&fytas, Gr.) A name 

 given to different stones of exces- 

 sive hardness, as to the diamond. 



ADAMA'NTINE SPAE. Imperfect corun- 

 dum; a variety of rhombohedral 

 corundum, nearly analogous to per- 

 fect corundum, containing from 3 

 to 5 per cent, of silica, and 1 to 2 

 of oxide of iron. 1 1 occurs massive 

 and in crystals. The crystals brought- 

 from India are the most pure. 



ADA'MIC EARTH. A name given to 

 red clay. 



