CHA 



CMA 



prefixed ; thus 10 chains 7 links must be 

 set clown 10.07. 



Then if the field be a square or paral- 

 lelogram, if you multiply the length ex- 

 pressed in chains and links, by the breadth 

 expressed in the same manner, and cut 

 off five figures from the product, those 

 towards the left hand will be acres ; then 

 multiply the separated figures by four, 

 cutting off the same number of figures, and 

 you will have the roods or quarters of an 

 acre ; and lastly multiply the remaining 

 figures by 40, cutting off" five as before, 

 and you will have the square perches. 

 See SCHVEYIWG. 



CHAINS, in a ship, those irons to which 

 the shrouds of the masts are" made fast to 

 the chain walls. 



CHAIN -walls, in a ship, the broad tim- 

 bers which are made jetting out of her 

 sides, to which the shrouds are fastened 

 and spread out, the better to secure the 

 masts. 



CHAIN 'shot, two bullets with a chain 

 between them. They are used at sea to 

 shoot down yards or masts, and to cut 

 the shrouds or rigging of a ship. 



CHAIN pump. See PUMP. 



CHALCEDONY, in mineralogy, a spe- 

 cies of the flint genus ; of which there are, 

 according to Werner, two subspecies, viz. 

 the common chalcedony and the carne- 

 lian: the colour of the former is grey in 

 all its shades. It is commonly semi-trans- 

 parent, harder than flint, brittle, diffi- 

 cultly frangible ; and the specific gravity, 

 according to Kirwan, is about 2.6. Infu- 

 sible before the blow-pipe. It is found 

 mostly in balls, in amygdaloid, also in 

 angular pieces and veins, in porphyry and 

 amygdaloid. The cubic variety occurs 

 in Transylvania, and the other varieties 

 in Iceland, the Feroe Islands, Silecia, Sax- 

 ony, Siberia, Cornwall, Scotland, &c. It 

 is susceptible of a fine polish, and is em- 

 ployed as an article of jewelry. It de- 

 rives its name from Chulcedon, in Asia, 

 where it was first found. Onyx is con- 

 sidered as the most valuable variety of 

 this species, and, on account of its be- 

 ing capable of receiving a high polish, 

 is very much prized. It is principally 

 cut in bas relief work, and the finest 

 specimens or that purpose are brought 

 from the East Indies. The dendritic 

 variety is named mocha stone, being 

 brought, originally, as was supposed, 

 from Mocha, on the Red Sea; but it is 

 now generally understood that the word 

 mooda is a corruption from the German 

 word mocks, which signifies moss; and 



it is affirmed that no stone of the kind is 

 found near Mocha. 



The principal colour of the carnelian is 

 blood red, of all degrees of intensity ; 

 from this it passes into milk-white, and 

 also into a kind of yellow. Semi-transpa- 

 rent ; and in many other of its characters 

 it agrees with the common chalcedony. 

 It is found accompanying agate, and, in 

 general, has the same geognostic situa- 

 tion as chalcedony. The fine oriental va- 

 rieties occur in rolled pieces. The 

 most beautiful carnelian is brought from 

 Arabia and liindostan ; it is also found in 

 different parts of Europe, and is used 

 for seals, bracelets, crosses, and other or- 

 naments. 



CHALCIS, in natural history, a genus 

 of insects of the order Hymenoptera : 

 mouth with a horny compressed jaw ; 

 feelers four, equal ; antennae short, cylin- 

 drical, fusiform ; the first joint a little 

 thicker; thorax gibbous, lengthened be- 

 hind in the place of a scutel ; abdomen 

 rounded and slightly petiolate. There 

 are eleven species 



CHALDRON, a dry English measure, 

 consisting of thirty-six bushels, heaped 

 up according to the sealed bushel kept 

 at Guildhall, London ; but on ship-board, 

 twenty-one chaldrons of coals are allowed 

 to the score. 



CHALK, in natural history, a species of 

 CALK, which see. 



Chalk, where it is found at all, is the 

 preponderating substance, and may there- 

 fore be considered as characterizing a 

 peculiar species of mineral formation. It 

 is perhaps the most recent of all the va- 

 rieties of calcareous carbonates ; it occurs 

 in strata for the most part nearly horizon- 

 tal, alternating with thin layers of flint 

 nodules, and with the same irregularity 

 dispersed through its substance ; it con- 

 tains in abundance the relics of marine 

 organized bodies, such as echinites, 

 glossopetrx, pectinites, &.c. and also not 

 unfrequently the hard parts of amphibi- 

 ous and land animals, as the heads and 

 vertebrae of crocodiles, and teeth of ele- 

 phants. Chalk hills never rise to a high- 

 er elevation than three or four hundred 

 feet, and are at once distinguishable by 

 the smooth regularity of their outline, 

 and their remarkable tendency to form 

 cup-shaped concavities. Ridges of chalk, 

 in England at least, are always bordered 

 by parallel ranges of sand or sand stone, 

 beneath, and alternating with which are 

 situated the beds of fullers-earth. Chalk 

 hills are also singularly characterized by 

 their drvness and their verdure : the most 



