REN 



336 



EES 



Rnnie. knowledge of pure mathematics is more easily acquired 

 s " > '"V""'' than that of any branch of science, or of useful know- 

 ledge ; and consequently, the possession of it indicates 

 no talent, and no genius of any kind. Those, therefore, 

 who have been early initiated into its abstractions, ex- 

 perience great difficulty in abandoning the results of 

 theory, and in throwing themselves entirely upon the 

 resources of experiment and observation ; while those 

 who have founded their professional acquirements upon 

 the great practical truths, which are often collected 

 from the experience of ages, have frequently rejected 

 the aid of theory, even in those cases where its assist- 

 ance might have been advantageously accepted. Like 

 all extremes, these two are to be carefully avoided ; 

 but that extreme is to be especially guarded against, 

 which would lead us to renounce those opinions of the 

 value of practical science, which, without naming any 

 living examples, are founded on the history of the lives 

 and labours of Bolton, and Watt, and Rennie. 



Although Mr. Rennie did not devote himself to the 

 acquisition of theoretical knowledge, excepting to that 

 general extent which is required by every well-inform- 

 ed engineer, yet he was fond of those investigations of 

 a mixed character, where the results of experiment 

 were combined by mathematical rules, and a train of 

 inquiry directed and modified by the lights of theory. 

 The writer of this article cannot forget the pleasure 

 which he one day afforded to Mr. Rennie, by giving 

 him a minute account of the beautiful results obtained 

 by Coulomb, respecting the resistance of fluids by his 

 fine application of the principles of Torsion. 



Rennie has been compared with Smeaton as an en- 

 gineer ; but the parallel is, in our opinion, not a cor- 

 rect one. Smeaton possessed much more theoretical 

 knowledge than Rennie, and Rennie surpassed Smea- 

 ton in his practical resources. The latter was more of 

 a man of science ; and, if he was less of a practical en- 

 gineer, we may ascribe it, in some degree, to his having 

 flourished at an earlier period of the arts, and at a time 

 when the military and naval resources of our country 

 were not called forth for its defence, and when British 

 capital, and British enterprise, had not dared to em- 

 bark themselves in works of national magnitude and 

 interest. 



If we could venture, at such an early period after 

 Mr. Rennie's death, when the adage of De morlitis nil 

 nisi bonum is in full force, to give an opinion upon hrs 

 works, we should be disposed to say, that they are 

 sometimes characterized by a massiveness, and, conse- 

 quently, by an expence which may not have been abso- 

 lutely necessary under all the circumstances of their 

 erection. The perfection of civil engineering must al- 

 ways be held to consist in the production of a work with 

 the least expence of labour and materials. In looking 

 forward to the ravages of time and of accident, there 

 is of course no point at which we can set limits to our 

 caution. The engineer may, with more propriety, 

 strengthen his bridge or his aqueduct against some fu- 

 ture assault of hostile cannon, than defend them against 

 .floods that never flowed, against pressures that never 

 pressed, or against winds that never blew. In contem- 

 plating the firmness of fresh granite, or the toughness 

 of newly-forged iron, we are apt to forget that time 

 corrodes and disintegrates both; and that diseases to 

 which even their obdurate nature is subject, some- 

 times unite their strength to that of the great de- 

 stroyer. If these observations have any force in regard to 

 works whose expence is defrayed out of the public 



treasury, their application must be still more pointed 

 to those of a commercial character, which have been (I 

 undertaken by individuals as an investment of their Res ' stance - 

 capital. Here the economy of construction ought to 

 be the principal object of the engineer, and a regard for 

 his own reputation, and even many public considera- 

 tions, ought to be kept in due subordination to that 

 leading object. 



Had it been our fortune to be a well-employed 

 engineer, we would have cheerfully witnessed the 

 failure of some favourite erections, provided we could, 

 at some distant period, be indulged with the sight of 

 the remainder balanced in skilful equilibrium, and ex- 

 hibiting their airy stability to the wonder and admira- 

 tion of succeeding ages. 



The caution of those engineers (among whom Mr. 

 Rennie cannot be placed) who habitually shelter their 

 scientific character under a mass of stone and iron, may 

 be compared to the prudery of some men of science, 

 who are exceedingly timorous of error, and who spend 

 their lives in polishing and working up some slender, 

 or perhaps considerable discovery. The bold and skil- 

 ful engineer, on the contrary, resembles those adven- 

 turous spirits who pant only after triumphs, and forget 

 the slips they may have committed in securing them. 

 The failures of the one, and the errors of the other 

 genius, are no doubt emblazoned for a while by contem- 

 porary or local malignity ; but time refuses to collect 

 the chaff which the breath of envy has raised, and pos- 

 terity takes cognizance only of those labours of genius 

 which never die. 



We have been led into these remarks solely with the 

 view of explaining the grounds of the criticism which, 

 with much hesitation, we have made on the character of 

 some of Mr. Rennie's undertakings; but this criticism, 

 even if it is a correct one, cannot be supposed to affect 

 our opinion of his pre-eminent merits as a civil engi- 

 neer. 



We are not aware that Mr. Rennie is the author of 

 any Memoir in the transactions of our learned socie- 

 ties. 



An excellent bust of Mr. Rennie was executed in his 

 life-time, by our great artist Chantry, and a good medal- 

 lion by Bain has been copied from it. The late Sir Henry 

 Raeburn also painted two excellent portraits of him. 

 Mr. Rennie had a fine commanding figure, and was of 

 a robust make, and greatly above the middle size. His 

 features were strong and large, and his expression mild 

 and agreeable. 



Various biographical sketches of Mr. Rennie have ap- 

 peared in our periodical works, and an eulogy upon him 

 was written soon after his death by M. Charles Dupin. 



RENT. See POLITICAL ECONOMY, in this volume, 

 p. 50. 



REPEATING CIRCLE. See CIRCLE, Vol VI. p. 4.98, 

 514. 



REPEATING CLOCKS and WATCHES. See HORO- 

 LOGY, Vol. XI. p. 145151, 



REPTILES. See HERPETOLOGY, Vol. XI. p. 1; 

 and OPHIOLOGY, Vol. XV. p. 452. 



REPUBLIC. See GOVERNMENT, Vol. X. p. 341. . 



RESERVOIR. See NAVIGATION, Inland, Vol. XV. 

 p. 309- 



RESINS. See GUMS, Vol. X. p. 556; and CHE- 

 MISTRY, Vol. VI. p. 108, 121- 128. 



RESISTANCE OF FLUIDS. See HYDRODYNAMICS, 

 Vol. XI. chap. v. p. 542 551 ; and PNEUMATICS, 

 Vol. XVI. p. 681691, 

 3 



