CIR 



CIS 



city of a revolving body, measured by an 

 arc of a circle. 



CIRCU'MFERENCE {circum fero, to 

 carry round). A line which bounds a 

 figure, commonly applied to curvilinear 

 figures. The Greek synonymous term 

 periphery is, however, applied to recti- 

 linear figures. 



CIRCU'MFEREN'TOR. An instru- 

 ment used by surveyors for taking angles. 



CI'RCUMFLEX VERBS. A term ap- 

 plied by Greek grammarians to those 

 verbs which are also called pure or con- 

 tracted because, after contraction, the o) 

 receives a circumflex, as (piXeto, <pi\(o. 

 See Accent. 



CIRCUMPO CAR STARS. Stars which 

 revolve round the pole, without setting in 

 a given latitude. The number of these 

 stars increases with the latitude of the 

 place, or the elevation of the pole above 

 the horizon. 



CIRCUMSCFSSILE (circum, around, 

 scindo, to cut). Divided around by a 

 transverse separation, as applied to that 

 mode of dehiscence of fruits which oc- 

 curs in hyoscyamus, in anagallis, in 

 lecythis, &c. 



CIRRHO'PODA {Kippb9, frizzled hair, 

 TToi/f, 7ra56p, a foot). A class of aquatic 

 invertebrate animals, with numerous la- 

 teral articulated cirrhi, and their body 

 fixed in a multivalve shell. The class is 

 composed chiefly of the barnacles and 

 acorn-shells. The following orders have 

 been distinguished : — 



1. Balanida, or those which are en- 

 closed in fixed, sessile, multivalve, coni- 

 cal shells, as the halanus. 



2. Anatifida^ or those which have the 

 enveloping shell attached by means of a 

 long fleshy contractile tubular peduncle, 

 as in the analifa. — Grant. 



CFRRHOSE {Ktppoi, frizzled hair). 

 Any thing which terminates in a tendril, 

 or filiform appendage, as the leaf of seve- 

 ral leguminous plants. 



CI'RRI (plur. of cirrus, a curl). The 

 curled filamentary appendages which re- 

 present the feet of the barnacles. 



CIRRI'GRADA [cirrus, a curled lock 

 of hair, gradior, to advance). A group 

 of the AcalephcB, the lower surface of 

 some of which is furnished with nume- 

 rous appendages, called cirri, which are 

 organs of pirehension, and, it is supposed, 

 of progression. 



CI'RRIPEDES {cirrus, a curi, pedes, 

 feet). A class of articulate animals, 

 having curled jointed feet. See Cirrho- 

 poda. 



79 



CIRRO-CUMULUS {cirrus, a curled 

 lock of hair, cumulus, a heap). The 

 sonder-cloud; an intermediate modifica- 

 tion of clouds between the cirrus and the 

 cumulus. It consists of extensive beds 

 of numerous small well-defined orbicular 

 masses of cloud, or small cumuli, in close 

 horizontal opposition, but at the same 

 time lying quite asunder or separate from 

 each other. The prevalence of this cloud, 

 in summer, forebodes an increase of tem- 

 perature ; in winter, the breaking up of 

 a frost, and warm and wet weather. 



CIRRO-STRATUS {cirrus, a curled 

 lock of hair, stratus, a bed or covering). 

 The wane-cloud ; an intermediate modi- 

 fication of clouds between the cirrus and 

 the stratus, distinguished by its flatness, 

 and great horizontal extension in pro- 

 portion to its perpendicular height. From 

 its generally changing its figure, it has 

 been called wane-cloud. Varieties of this 

 cloud occur in the mackerel-back sky of 

 summer evenings ; and in the cymoid 

 modification, which consists of small rows 

 of little clouds, curved in a peculiar man- 

 ner. The prevalence of these clouds is a 

 sure sign of rain or snow ; the cymoid 

 variety always indicates stormy weather. 



CFRRUS (Lat., a lock of hair curled). 

 The curl-cloud ; a primary form of clouds, 

 characterized by its curling and flexuous 

 form, by the lightness of its appearance, 

 its fibrous texture, and the great and 

 perpetually changing variety of its figure. 

 It accompanies a variable state of the 

 weather, and forebodes wind and rain. 

 The comoid cirrus, vulgarly called mare's 

 tail, is the proper cirrus ; it resembles a 

 distended lock of white hair, or a bunch 

 of wool drawn out into fine pointed ends. 

 Modifications of this texture occur in the 

 linear cirrus, in which the lines of cloud 

 are parallel ; and in the reticular cirrus, 

 in which they cross each other in various 

 directions, presenting the appearance of 

 net-work. 



CI'SSOID (Kio-o-of, ivy, 6i3of, likeness). 

 Resembling ivy; a fanciful designation 

 of a curve line of the second order, em^ 

 ployed by the Greeks in the celebrated 

 problem of finding two mean propor- 

 tionals between two given straight lines. 



CISTA'CE^. The Cistus or Rock- 

 rose tribe of Dicotyledonous plants ; 

 characterized by the fragrant resinous 

 secretion of their leaves, the beauty of 

 their fugitive flowers, and the produc- 

 tion, from some of their species, of the 

 green labdanum. 



CISTE'LIDES. A family of Coleopte- 

 E4 



