CIRCASSIA. 



practice in Circassia for widows to tear their but these all are obliged to take the oath of allegiance Cireania. 



lii-tigur-.' themselves wr. totim .ny to his imperial majesty; they administer justice in his "V""'*' 



of their rr. icss of their husbands. It was for- name, and, in matters of importance, not without the 



. ic men al>, to give way to similar expres- presence of the Russian governors. See Tooke'l ( tf'a 



sions of so> row ; but of late they have griwn much more 

 .il under the los- of their wires, or of other relations, 

 f cilr of Circassia it Terke. The prince 

 who reside* here is allowed a guard of 500 Rutsians, but 

 ;rct is suffered to dwell within the 

 since the time that this country 

 was ubdued by Russia, not only governors and garri- 

 sons of that nation have been appointed to all places of 

 strength in it, but it has been provided from the same 

 quarter with its magistrates, and with priests for the ex- 

 ercise of the Christian religion. In subordination to the 

 supreme authority of Russia, the Circassian Tartars ac- 

 knowledge indeed their own princes, lards, and judges ; 



presence o tn- n- 



at' the Uustian Empire ; Kill*-.'* Journey through Ike 



', &c ; and Clarke's 

 Trin els in Kiirone, Asia, anil Afrirn, vol. i. (K) 



CIRCENSI AN i Mgiually called Conrualia, 



were dcdic iteii to the '."J COIIMIS, and were established by 

 Romulus at the rape of the Stbines. After the Circus 

 was built by Tarquin the Klder, they received the namo 

 of Circensian games. The celebration of these games 

 began on the 15th S-pti-mber, and continued live days ; 

 and they consisted in feats of leaping, boxing, wrestling, 

 racing both in chariots and on foot, and throwing the 

 javelin and quoit, (j) 



CIRCLE. 



Circle. ^ ASTRONOMICAL CIRCLES having now entirely superse- 

 '""""V'"''' ded the use of the quadrant, and become the principal 

 instruments of almost every observatory, we feel our- 

 selves called upon to devote a considerable portion of our 

 work to the explanation of the principles of their con- 

 struction, and of the most eligible methods of wing them 

 to advantage. 



The astronomical quadrant is so .simple in its construc- 

 tion, and one instrument of this class differs so little from 

 another, that the description of one will easily render in- 

 telligible the construction of all the rest. It is not so, how- 

 ever, with the astronomical circles. So very various have 

 been the views and conceptions of the different artist*, who 

 have been employed in these instruments, and perhaps even 

 of the same artist at different times, that, except in circles 

 of small dimensions, we believe that two have never yet 

 been made alike. Hence we find no small difficulty in 

 selecting such examples as may be reasonably expected 

 to continue of universal and permanent utility. 

 CircW The circle of Piaz/i, at Palermo, constructed by Mr 



r *>y Ramsden, was the fust large instrument of modern con- 

 struction, and has become justly celebrated in the hittory 

 of practical astronomy ; but it owes its celebrity certain- 

 ly more to the industry and sagacity of the observer into 

 whose hands it has fortunately fallen, than to the accu- 

 racy or soundness of the principle!) on which it is con- 

 structed ; for though it contains numberless examples of 

 beautiful invention and contrivance, yet upon the whole 

 it is an instrument that no judicious artist would ever 

 wish to make again : We shall not therefore detain the 

 reader with any particular description of it, but shall on- 

 ly observe, that it is an altitude and azimuth instrument. 

 The diameter of the vertical circle is five feet. The plumb- 

 line by which it is adjusted, referring to two fixed points 

 in the limb of the circl- , cannot be examined at the mo- 

 ment of observation : From this cause, and from the effect 

 of expansion, to which, from its faulty construction, it is 

 much exposed, a single observation cannot be relied mi, 

 i than to five seconds, though a mean of several will 

 probably be much within that limit. In the year 1793, 

 WolU- _ ton published a description of a circlo made 



u" 1 for him !>) Mr Carry, and which he very properly t-imi 

 '* a Traiuit Circle, flu, imtrumcnt had an acc.dentai dc 



by Carey. 



feet, (the axis having been, made rather to.i slender,) Out 

 with this exception the instrument was a very good one. 

 The beauty of the workmanship of Carey's instruments 

 cannot be surpat ed ; and the whole of this imtrunv nt 

 was better imagined, than the large cue above noticed of 



Ramsden. It was not, however, intended to turn freely 

 in azimuth, but, on the contrary, principally designed as 

 a transit instrument, which intention appears to have been 

 accomplished with the greatest precision. For this prac- 

 tical success of combining two instruments in one, astro- 

 nomers are certainly much indebted to Mr VVollaston. 

 Piazzi, in enumerating the advantages of a circle, men- 

 tions this combination : hut certainly his circle would be 

 a very imperfect transit instrument, or more properly 

 speaking, it would be absolutely useless in this capacity. 

 Carey has constructed several of these instruments, which 

 perhaps would be all improved by a very slight alteration 

 in the mode of applying the plumb-line. His method is 

 nearly similar to Ramsden's above noticed, and subject to 

 the same objection, as will be better understood when 

 we come to treat of the more detailed construction of 

 particular instruments. It is in this circumstance (among 

 many others) that Troughton's instruments differ from 

 Carey's and Ramsden's. The principle of the>e two me- 

 thods is thus shortly described by Mr Pond, in the Phi- 

 lotophical Transactions for 1806. 



In Mr Ramsden's method two points are taken on the 

 limb of the circle ; and when these are brought into a 

 given position, by means of a plumb-line pissing over 

 tin 1 m, the microscope or index is made to coincide with 

 the zero point of the divisions. By this method the er- 

 ror in collimation remains constant ; and if the adjust- 

 ment is by any accident deranged, it can easily be recti-. 

 fied, and there will be no absolute necessity for frequent- 

 ly reversing the instrument ; so that this method seems 

 well adapted for large instruments, particularly if placed 

 on stone piers. But it is liable to this delect, that tho 

 adjustment cannot be examined at the moment of obser- 

 vation ; and if any change should take place in the gene- 

 ral disposition of the trame-work, the bscrvatLn will be 

 erroneous, with. -tit the means of detection It .'.as pro- 

 bably to avoid this inconvenience, that Mr Troughton in 

 most of his instruments, particularly it t i \ were intended 

 to move freely in azimuth, has preferred the other method. 

 In this case, the plumb line is att;u ed to ne of t'i'- 

 pillars which support the micro.' c :]/. s> in the way 

 described; and it has no relereno- to a y fix -d p< 

 divisions on the limb of the circle, hut only insur 

 m larity of position in the index for " n ' 1'ie 



instrument; and providedtli.it the plumb l>n. a; JMI .1119 

 was free from all danger of derangement, tin. w m!.! he 

 sufficient. This ve.nhe.m. n may perhaps be r. mlrrcd 

 more intelligible, by considering th.it a circular iubtru- 



4 



Circle. 



n.imidtn' 

 method uf 

 applyinr 

 llie plumb- 

 line. 



Trough- 

 ton tme- 



iluid. 



