THE 



CIVIL ENGINEER AND ARCHITECT'S 



JOURNAL 



INTRODUCTORY NOTE. 



In commencing the lOOlh I'art, and a new volume of this work, the con- 

 ductors of it venture upon a few introductory remarks ; the object pro- 

 posed is not, however, merely to offer the courtesies of salutation, though, 

 were it no more, we might well be excused — at a season of universal 

 greeting and goodwill — for expressing to those who have accompanied 

 us, and those who have assisted us in the prosecution of our task, with 

 how much gratification we arrive at this epoch of it, and commence a new 

 portion of our labours. 



In a periodical devoted, not to the general purposes of literature, but to 

 the publication of information on specific subjects, and these of a very 

 extended and frequently complicated nature, the reader has a right to 

 expect that the mode of selecting and communicating information should 

 be guided by certain fixed principles ; for it is certain that, were no other 

 rules adopted in conducting such a work as this, than that of setting down 

 whatever appears to possess a passing interest, and that of recording the 

 information just as it is supplied to us, the reader would no longer find 

 what he would most anxiously seek for in these pages, professional in- 

 formation selected for its intrinsic importance, and referred to certain 

 fixed principles as tests of its value and accuracy. 



In Engineering, the first branch of ourlabors, it is by no means difficult 

 to explain the rules here adopted. The theory of the operations of the 

 engineer belongs, fortunately, to a philosophy the most accurate and 

 complete, of all which the range of human thought encompasses — the 

 philosophy of motion and equilibrium ; and the application of this phi- 

 losophy to practical mechanics is founded on a system of experimental 

 knowledge, far exceeding in extent and the uniformity of its results 

 all that has been obtained in other practical arts. For while, on the 

 one hand, none of the operations of nature have been so successfully theo- 

 rised as the mechanical, and on the other, none have been made so gene- 

 rally the subjects of practical industry. 



In examinining, then, the labours of the engineer and mechanist, we 

 have first to see how far their notions accord with the pure theory ; se. 

 condly, how far the details of their works stand the test of experience. 

 There once prevailed, unfortunately, an idea that the theory and practice 

 of mechanics were inconsistent with each other ; but the new and constantly 

 increasing requirements of modern engineering are now fast dissipating 

 the error ; for, while the theoretical student finds it impossible to render 

 his knowledge available without actual experience, the practical ope. 



Mo. 100.— Vol. IX.— Januaby, 1846. 9 ) <- 



rator frequently finds, from the rapid advances of modern engineering, that 

 he is placed in circumstances altogether new to him — discovers that his 

 notions of the laws of mechenics picked up here and there, without any 

 system, and generally mixed up with a vast amount of extraneous matter 

 will nut always suffice, and that he must frequently submit his judgment, 

 in a measure at least, to that af the theorist. 



It is quite true that the actual operations of engineering generally de- 

 pend on natural laws so complicated as to render direct mathematical 

 investigations, either impossible, or rendered possible only by hypothe- 

 tical simplifications of the cases examined. It is not, therefore, to the 

 immediate results of mathematics, that we are to look for the most general 

 benefit derivable from pure theory, though even here how much has been 

 done for the assistance of the engineer, labours such as those of Coulomb, 

 Poncelte, De Pambour, Hodgkioson, Moseley, and Professor Willis 

 amply testify. But there is another far more common benefit which the 

 engineer will derive from mathematical knowledge, which, if duly con- 

 sidered, ought to remove from the mind of the practical student sU coldness 

 and suspicion respecting the results of theoretical mechanics. 



It is not to be expected that an engineer, however high his mathema- 

 tical attainments, could determine, numerically, the velocity of every 

 engine he constructs, the pressure on every tunnel, or revetement wall 

 which he builds ; but this is certain, that his mathematical education will 

 have so systematised and simplified his mechanical conceptions, ihat he 

 will examine his works far more critically than he possibly would, were 

 his physical notions derived merely from his own experience or popular 

 treatises. It may be unhesitatingly affirmed that the perspicuous general 

 insight into the laws of mechanics, afforded by the study of mathematics, 

 is not tt be obtained by discursive reading and casual experience how- 

 ever exle.'sive or varied in ils nature. It were easy enough to give in- 

 stances of men eminent for their practical labours, who, from lack of syste- 

 matic knowledge, frequently utter notions the most confused on mechanical 

 subjects ; or — to refer to more immediate instances — we might, from our 

 own pages, point out repeated cases of inventors obtaining patents for the 

 supposed attainment of physical impossibilities. 



That chief value of the mathematical theory of mechanics to the prac- 

 tical engineer would seem then to be, not so much the prediction of the 

 exact result of his labours, as the general guidance afforded to him in 

 conducting them — the knowledge by which, without the toil of experi- 

 ment, he distinguishes between what is physically possible and what im- 

 possible, and is directed in choosing the mechanical appliances best suit- 

 able to effect his objects. Who can estimate how vast an amount of intel- 

 lectual and experimental labour might have been saved, had thoet who 



