T R A 



T R A 



thel'e tv/o times, vix. i^ zi"" Hi', will be the difference of 

 the obfervcd time of their tranfits, owing to the error of 

 the poiitiou of the tranfit-telefcope, their real right afceu- 

 fion beincr fuppofed the fame." After having thus given 

 iir H. Englefield's own words, we (hall only add on this 

 fubje<ft, that on enquiry of Mr. Thomas Jones, we learn 

 that feveral of thefe inftruments have been made and fold, 

 and one on an enlarged fcale ; but that rtars fmaller than 

 thofe of the third magnitude cannot be feen by a telefcope 

 in which the refleftion precedes the refraftion. 



TRANsiT-C/rc/i', is an aftronomical inilrument, by which, 

 with the aid of an aftronomical clock, both the right af- 

 cenfion and declination of a heavenly body are determined 

 at the fame time. This inilrument is of modern date, and 

 differs from a tranfit-inftrumentof the beft conftruftion, only 

 as it has a graduated circle of larger dimenfions than the latter, 

 and, by means of microfcopes, reads the angle obferved to 

 the accuracy of 3, fwgle fecond ; whoever, therefore, has a 

 l^ood tranfit-circle, and a fuperior aftronomical clock, has 

 an obfervatory for determining the exaft place of any hea- 

 venly body. Under our article Circle, we have defcribed 

 the mural tranfu-cirrle by Troughton, which has been ufe- 

 fully employed by Mr. S. Groomb ridge at Blackheath, and 

 which has proved itfelf to be an inftrunient of the firft clafs ; 

 ::nd we there ftated a report, that a large one was in contem- 

 plation for Greenwich, which we faid we might poITibly 

 have occafion to defcribe. That inftrumcnt has been finifhed 

 by Troughton in his beft manner, and though the plan of 

 the conftruftion is unique, and the mode of ufing it novel, 

 its application to the purpofes for which it was intended 

 anfwers the moft fanguine expeftation of the maker, and 

 in the hands of the prefent aftronomer-royal, affords the 

 means of making more accurate and at the fame time more 

 numerous obfervations in a given time, than ever were 

 cft'cfted by any other inftrument. Though this inftrument 

 has a long axis paffing through a folid pier of mafonry, ajid 

 is capable of being ufed for tranfits, it has hitherto been 

 principally ufed for determining polar diftances, by aftual 

 mcafuremcnt from the polar point ; according to which 

 mode, the uncertainty in the rcfults, which commonly arifes 

 from variable refraftion in ordinary meafurements, is almoft 

 entirely obviated, and a repetition of any feries of obferv- 

 ations may be made on any part of the circle ad libitum, 

 and with any number of readings to the number of fix at 

 the fame time ; fo that a fingle obfervation is made with as 

 much accuracy, as can be obtained from an average of 

 feveral fucceffive obfervations taken with a repeating-circle 

 of the fame dimenfions ; and yet there is the power of re- 

 peating any obfervation in various pofitions. Mr. "Pond has 

 already pubhftied one volume of obfervations taken with 

 this inftrument, which completely verifies our affertions, and 

 in this firft volume he has given a plan and feilion of this 

 inftrument, the circle of which is fix feet two inches in 

 diameter ; but as Mr. Troughton intends to give a complete 

 defcription thereof himfelf, as a paper fuitable for the 

 Philofophical Tranfaftions, which, to be publiflied tlierein, 

 muft be an original communication, Mr. Pond was not at 

 liberty to defcrihe the drawing which he has given as a 

 frontifpiece to his firft volume ; and as the defcription in 

 queftion is not yet finifhed, we are in the fame predicament 

 with the aftronomer-royal, and muft confequently for the 

 prefent forego the pleafure we had promifed ourfelves, of 

 introducing this magnificent inftrument to the notice of the 

 pubhc. 



TRANSITION, in Mufic, is nearly fynonimous with 

 modulation ; it implies little more, in its technical ufe, than 

 a change ; and, in general, a change of key, from major to 



12 



minor, or the contrary ; or, indeed, from any one genus or 

 key to another. Luckily no laws were laid down by our 

 forefathers for tranfition, as for modulation, which we fo 

 long feared to violate. 



Transition, in Rhetoric, a kind of conneAiou in dif- 

 courfe, by which tlie feveral different parts and members of 

 it are joined, fo as to conftitute one regular whole : or, 

 as VofTius defines it, it is a form of fpeech, by which the 

 fpeaker, in a few words, tells his hearers both what he has 

 faid already, and what he next defigns to fay. Sometimes, 

 however, in pafling from one thing to another, a general 

 hint of it is thought fufficient to prepare the hearers, with- 

 out particularly fpecifying what has been faid; or is next 

 to follow. 



Some place tranfition in the number of figures ; others, 

 with Quinftilian, exclude it from that rank. 



F. de Colonia makes two kinds of tranfitions, the one 

 perfed, and the other imperfed. 



Transition, PerfeB, is that in which we briefly inti- 

 mate what is faid, and what remains to be faid. As, No-u> 

 that we have fpoken of -war, there remains fomething to be faid 

 oj peace. Satis multa de turpiludine : dicam deinceps, quad 

 propofui, de periculo. Uni epiflolie refpondi : venin ad alteram. 

 Sed hue -Vetera ; illud recens : Cdfarem meo conftlio interfeSum. 



Transition, Imperfed, is that in which only one of 

 thefe is exprefled. As, Let us now confider the confequences 

 of, iffc. Poflularel hie locus, ut dicerem de — fed finis fit ; nc- 

 que enim pree lacrymis jam loqai poffum ; et hie fe laerymis de- 

 fendi negat. 



Transition Rocks, in Geology, a name introduced by 

 Werner to defignate thofe rocks which, on account of their 

 containing few organic remains, and lying immediately over 

 other rocks which contain none, are fuppofed by him to 

 have been formed when the world was pafling from an un- 

 inhabitable to a habitable ftate. According to the fame 

 geologitl, tranfition rocks are of more recent formation 

 than the lower or primary rocks, and older than the floetz 

 or ftratified rocks, and are intermediate between both, be- 

 ing partly of mechanical and partly of chemical formation. 

 The rocks which are enumerated in this clafs by Werner, 

 are tranfition lime-ftone, tranfition trap, greywacke, and 

 flinty flate. It is now, however, admitted, that the dif- 

 tinition made between tranfition rocks and the lower ftrati- 

 fied or flcetz rocks, has little or no foundation in nature, as 

 thefe rocks are not unfrequently obferved to alternate with 

 each other. ( See Rocks. ) Nor is the abfence of organic 

 remains in the lower rocks, called />W;«a/-_)', a decifive proof 

 that they were formed previoufly to the exiftence of organic 

 life upon our planet ; for in a feries of ftratified rocks con- 

 taining organic remains, we frequently meet with other beds 

 interpofed, in which no veftige whatever of fuch remains 

 can be traced. Hence we may infer, that the procefs by 

 which the latter was confolidated, has deftroyed the organic 

 matter which they may have once contained. The abfence 

 of organic remains in filiceous beds that have a cryftalline 

 granitic ftruclure, is, we conceive, owing to the peculiar 

 mode by which they were cryftalHzed, as fuch beds fome- 

 times repofe on other beds abounding in marine fhells. Nor 

 can we be certain, that the loweil rocks of granite were 

 formed before the exiftence of animal life on our planet. 

 The more extenfively modern geologifts have carried their 

 obfervations, the more numerous are the inflances found of 

 marine fhells or vegetables occurring in alpine diftrifts 

 formerly regarded as primary ; and if granitic rocks, wher- 

 ever they occur, are invariably deftitute of extraneous foffils, 

 we mufl attribute it to the peculiar mode of their forma- 

 tion, rather than to their priority of age. 



The 



