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Jie fiipprcfs tlie movements of felf-gratiilatlon, wliicli tlie 

 confcioiifncfs of his powers and acquirements excited in liis 

 bread. By liis pcrfiiafioii, Noccti, his mailer in philofophy, 

 was induced to reprint a fniall poem on tlie rainbow, and 

 another on the anrora borealis, both of which Bofcovidi 

 enriched with ingenfons notes and ilhillrntions. 1"he pnb- 

 lication of tiiis trail fpread his fame beyond the preeinds 

 of tlie college, and beyond the Alps. Mairan, whofe opinion 

 concerning the aurora borealis he had efpoufed, noticed it 

 with loud commendation, in the fccond edition of liis dilfer- 

 tation ; and the praifes bellowed by the French philofopher, 

 with the title conferred on him of correfpondent of the 

 Academy of Sciences, cnnld not fail to prove highly grati- 

 fying to his youthful vaiiity. 



After Bofcovich had completed tlie ufual courfe of phi- 

 lofophy, he was obliged, by the rules of the inilitution, to 

 teach grammar and the claflics ; but lie never loll light of 

 his favourite iludics, and lie was invited by his mathematical 

 mailer, to deknd annual the'fes, and deliver public dilTeita- 

 tions on fueli fnbjefts as occalion fuggcfted. Thefe being 

 printed in fiiccefiion, extended farther his reputation. The 

 tirll appeared in 1736, and contained a theory of the folar 

 fpots, very llmilar to that which was afterwards fo inge- 

 nioudy f.ipported by profelTor Wilfon, of Glafgow. It 

 fnppofes the fun to have two atmofpheres, the lower licing 

 dciile, and fometimes fprinlcled with clouds ; the upper rare, 

 and fubjirtl to variation of height. Next year produced 

 two dilfertations ; one on the tianlit of Mercury, and ano- 

 ther on a remarkable aurora borealis. 



Five years had Bofcovich fpent in the drudgery of teach- 

 ing Latin, and three more were confumed in the unprofitable 

 ftudy of fcholaflic theology, when, by a very fingular indul- 

 gence, he was cxeinpted by his fuperiors from the fourth 

 year's attendance, and permitted to rclinquilb that dark, and 

 thorny path, and thenceforth employ his talents in exploring 

 Nature's wide domain. His fituation now, as fupernu- 

 merary prefect of the Roman College, was entirely fuited to 

 his talle. To communicate mathematical inllruftion was 

 to him a delightful talk ; and he prepared, for the tife of 

 his pupils, a fhort fyllem of geometry, which comprized all 

 the capital truths of that fcience in fourteen propofitions. 

 In the fcledlion of the materials, in their difpolition and 

 arrangement, he exhibited the clearnefs, the precifion, and 

 noble elegance, formed after the model of the ancients. He 

 compofed the elements of trigonometry with the fame purity 

 of talle. But the capital part of the fyllem, his theory of 

 the Conic Scftions, was reared by repeated efforts, and at 

 dillant intervals, and was not publilhed until the year lyjv 

 Bofcovich conlidered thefe curves as defcribed in piano, 

 and alfumed, for his generic definition, the beautiful pro- 

 perty of the i/lrecfi-i.x, which is common to them all, the 

 parabola being only its fimpleft cafe. In the ellipfe, the ratio 

 of a line, drawn from any point to either of the foci, is to a 

 perpendicular from the fame point to the i/ire/7rix, in the 

 ratio of a lefs to a greater ; in the hyperbola, it is that of a 

 greater to a lels. But the author did not Hop here ; he 

 likewife invelligated the properties derived Immediately from 

 riie feftion of the cone. He fuppofed it cut by a moveable 

 plane, and (howed how the feveral curves would thence be 

 fucceffively produced. The fame luminous idea he trans- 

 ferred to the cylinder, the fpheroid, and the conoids. His 

 imagination loved to contemplate the fine mutation and 

 tranfition of mathematical figure, and to trace the feries of 

 fucceffive, yet apparently conneAed changes, which have 

 fuggelled the law of continuity. On that metaphyfical prin- 

 ciple, as elucidated by the transformation of geometrical 

 loci, he gave an exquifite differtation. Other differtations, 



Vol. V. 



BOS 



remarkable for their ingenuity, were fucctflively d.-Iivcrcd 

 to a crowded audience, at the annual examination of hie 

 Icliool, Thefe treated ou various difficult points in geome- 

 try, 3llrciioniy,and optics ; on ofculating circles, the nature 

 of infiuitelimnls, Irajcflories, the inecjiuilitv of gravity over 

 the earth's furface, the centre of magnitude, the lav.s of 

 bodies, living forces, the flux and rtiliix of the fea, the 

 annual abt nation of the fixed ftars, the limits of allroiiomica'l 

 obfi_rvalioiis, the ufe of knfes and dioptric tclcfcopes, and a 

 new nitthod of employing the obftrvation of the phafet in 

 lunar eclipfes, on the dctciniination of a planet's orbit, bv 

 help of catoptrics, and on the atmufphere of the moon, 

 which he held to be very different from that of the earth, 

 and more analogous to water. In one of thefe diflertations 

 he pointed out a mlilake of the famous Daniel iWrnouilli, 

 who had liaflily coneludtd, that the tides of the atiiiofiihere 

 mull rife higher, in proportion to its rarity, than thofe of 

 the ocean ; in another, he fliewed that the qncllion, con- 

 cerning the mcafure of forces, which then fo vehemently 

 agitated the fcientific world, as it generally happens, was 

 merely a difpute of words ; in a third, he (Icetched the out- 

 lines of that bold ftruftuie, wliich has obtained fuch dcferved 

 celebrity among the learned — his fublime theory of the con- 

 flitution of matter. 



Wliile Bofcovich was thus ufefully and honourably en- 

 gaged in direding the lludits of youth, and enlightening 

 the learned world by his elegant and ingenious writings, the 

 pleafure of his convcrfation was eagerly courtijd at Rome. 

 In every houfe of note he was always a moll welcome guell, 

 and he reigned in every focitty by the afcendancy of his 

 talents. Before mixed companies he would freely talk of 

 his own fpeculations, which he had a fingular felicity in 

 rendering intelligible and interelling to the mod ordinary 

 minds ; and though, on thefe occalions, he was not accuf- 

 tomed to conceal his inward fatisfaction, or decline bellowing 

 upon himfelf the merited encomiums, thefe frequent fallies 

 ot vanity feenied to flow merely from the warmth of his 

 charafltr, and v/ere effaced in the general blaze of admiration 

 entertained for his fuperior talents. Nor was his ambition 

 confined within the circle of abllracl fcience ; indulging the 

 excurfive flights of fancy, he often facrificed to the Mufes, 

 He compoled I^atin verfes, on a great variety of fubjetls, 

 and which confequently pofTefTcd very different degrees of 

 merit. Every occurrence he was ready to feize, whether 

 public or private, ferious or comic ; wars, nuptials, jocular 

 and domellic incidents, were all indifcriminately his theme. 

 He had a wonderful knack in compofing thofe verfes, with 

 a memory not lels aftonifhing for retaining them ; and at the 

 tables of his friends he took pleafure in reciting elaborate 

 piiffages. Surrounded by his difciples and partial admirers, 

 the fort of idolatry which he received appears, however, to 

 have had rather an unfortunate efTeA on his charadter, by 

 tempting him to overrate the meafure of his powers, and 

 extent of his attainments. Once, and onae only, he entered 

 the lills with his illullrious contemporaries. It was in an- 

 fwer to the quellion, propofed by the Academy of Sciences 

 at Palis, to determine the iiiequahties produced by the 

 mutual aftion of Jupiter and Saturn, efpecially near the timr 

 of their conjunction. His memoir was returned with much 

 commendation, and very few mathematicians alTurcdly would 

 have felt themfclves lowered in yielding the premium to tho 

 great Fuler. But Bofcovich was piqued at what he con- 

 ceived to be an unfair decifion, and would never afterM'ards 

 engage in any public competition. 



A philofopher, refiding in Rome, amidfl the venerable 

 remains of ancient fplendour, was powerfully drawn to exa- 

 mine thofe jnonuments. Bofcovich wrote feveral difftrta- 

 L tioii* 



