1840.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



S9 



youths ?— those best will be able to decide, who can^ coolly give 

 itteraiice to such preposterous delusions. 



As to the manner in which they are supported by the profession, it 

 may perliaps be sufficient to refer to the men connected with it, but 

 we have farther public testimonials in the declarations of the Institu- 

 tion of Civil Engineers. The liberality of their opinions we have 

 already shown, so that anything emanating from them, carries with it 

 the whole vpeight of their character, and is free from the imputation 

 of interested motives. Their Report for 1S37,* while advocating 

 the necessity of supplementary instruction, states that nuich has at 

 times been said respecting the establishment of a School of Engi- 

 neers, and many comparisons have been drawn betwixt the advan- 

 tages possessed by this and other coimtries in this respect, but not 

 for an instant to enter on the great question of the nature of a com- 

 plete establishment under that name, it may with confidence be 

 asserted, that this histitution is in itself a School of Engineers- 



school not in the sense of the term wli 



knowledo-e is forced upon 



the imwilling student, but one where the attentive student ])ossesses 

 remarkable opportunities of self-improvement by study and mutual 

 intercourse. In the speech of the President, on opening the Session 

 of lS39,t he calls upon the members to improve themselves, not by 

 collegiate instruction, but by mutual improvement; he says, "there 

 is now upon the table, a prospectus for tlie establishment, on a large 

 scale, of a College for Civil Engineers," leaving his hearers to form 

 their own opinions upon the merits of such proposition. 



That there is room for the establishment of a school of engineering 

 on sound principles, it admits no question; but its sphere, although 

 extensive, is very dilferent from that contemplated by the present 

 plan. Its advocates jump at once to conclusions, inspired by (he 

 ardent hope of obtaining large premiums, they jumble everthing 

 together, and mix up the practicable with the impracticable. Ste- 

 phenson or Brmiel carry on no trade in jn-emiums of live hundred 

 guineas, it would make little diminution in their incomes, if they 

 had no pupils at all, but young men are sent to them because from 

 their emj)loyment in large works, they have great facilities in artbrd- 

 ing instruction, and ample means of employing them afterwards. If 

 the council of the College want to know what to do with their 

 establishment, we can tell them how it may be made useful to the 

 public, and profitable to themselves and their pupils. Let them re- 

 quire that every pupil in civil mining, marine or practical engineering 

 shall be articled to a practitioner, and let them like Universitj', King's, 

 and Durham Colleges, limit themselves to teaching the theoretical 

 branches. Form a special class for instructing steam vessel engi- 

 neers, and they may claim a government grant and a c'ass for locomo- 

 jive enpineers, and raihvay companies would probably contribute. Edu- 

 cate surveyors, and instruct them in the higher branches of geodesiacal 

 operations, not as planned by the College, merely the rudiments of iis- 

 tronomy, but its application in trigonometrical surveying. Give sup- 

 plementary education to mining engineers, and train up mineralogists 

 and assayists. Teach like King's College, the literature of manufac- 

 tures and machinery, but let the pu)uls study in the factory instead 

 of the toy-shop. Do the same for the manufacturing chemist, 

 London has establishments enough for his practice. Let the Univer- 

 sities or the Institution give the diploma, and limit the College to 

 teaching, and still will be done more than enough for a beginning, 

 and what will amjily pay for all expenses. 



In concluding these remarks, we cannot too strongly repeat, that 

 parents should hesitate before they compromise the interests of their 

 children, by sending tliem to this establishment, anfl we call on its 

 managers to pause in their career, before they have yet excited the 

 open hostility of the profession, and to devote their energies to a 

 useful and rational purpose, before they arc crushed by a powerful 

 opposition. We have been influenced by no prejudice against the 

 College or its objects, but we feel that we have best done our duty 

 both to it and our readers, by unsparingly denouncing what we con- 

 sider an erroneous and ineBicient system of education, and a certain 

 delusion to those who have the misfortune to be its victims. 



"'See vol.i.p. 138. 

 t See Vol. ii. p. 3. 



Oxford Viiiversiti/. — Feu' persons are aware that 100,000/. was loft to the 

 University of O.xiord by Michael Anpjelo Taylor, to build a picture gallery 

 and lecture rooms connected with science anil arts. A dispute having arisen 

 between his relatives and the trustees respecting the will, the latter, rather 

 than risk a suit in Chancery, have agreed to take 7.5,000/., and have bcgiui 

 clearing the foundation fcr the buildmg. They have removed the old houses 

 at the corner of Beaumont-street, St. Giles's, nearly opposite St. John's col- 

 lege, which J5 the most central they could meet with. 



GENERAL THEORY OF THE STEAM ENGINE. 



By Aristides A. Mornay, lisii. 



No. V. 



On the Action of the Steam in (he Cylinder (continiKd.) 



In our last numberwe demonstrated that the pressure exerted by the 

 steam against the piston may be assumed in practice as equal to its 

 full elastic force ; we intend in a future paper to enter into an investi- 

 gation of the elastic force of the steam at difierent instants during the 

 stroke of the piston, preparatory to which it will be necessary to in- 

 qviirc into the eHects of an arrangement, which exercises a material 

 inttucnce on the elastic force of the steam during a portion of the 

 stroke of the piston when it is adopted : we allude to the lead of the 

 slidt, which is considered indispensable in Locomotive Engines. 



The lead is the advance given to the motion of the sliile, by which 

 it is caused to shut the eduction port, and open the steam port a little 

 before the commencement of the stroke, and to sliut the steam port 

 and open the eduction port a little before the end of the stroke. 



In order to explain the reasons assigned for giving a leatl to the 

 slide in locomotive engines, we think we cannot do better than quote 

 the following from the description of Stephenson's Patent Locomotive 

 Engine, in Wcale's splendid edition of " Tredgold, on the Steam En- 

 gine," pages lot) ami 4.51 of the Appendix. " It is found necessary 

 to let the steam on to the opposite side of the piston before the end of 

 the stroke, in order to bring it up gradually to a stop, and diminish 

 the violent jerk that is caused by its motion being cliauged so very 

 rajjidly as five times in a second. The steam, let into the end of the 

 cylinder, before the piston arrives at it, acts as a sining cushion to 

 assist in changing its motion, and if it were not apjilieil, the piston 

 cotdd not be kept tight upon tlie piston rod. A little lead of the slide 

 is also necessary that the steam may be admitted through the port 

 into the cylinder, and be completely ready to begin the next stroke 

 when the piston is at the end of the cylinder; but so much is not ne- 

 cessary for this. 



"The principal advantage gained by giving lead to the slide is in 

 beginning to get rid of the waste steam before the commencement of 

 the stroke; so that when the piston commences its stroke there is but 

 little waste steam before it to resist its progress, the steam beginning 

 to be let out of the cyliniler before it has driven the piston to the end 

 of the stroke. This is a very important point in a locomotive, as the 

 resistance or negative pressure of the waste steam upon the piston is 

 very considerable ; from the rapidity of the motion, which allows very 

 little time for it to escape, and from the use of the blast pipe, which 

 obstructs its passage. The area of the extremity of the blast pipe is 

 only five square inches, while that of the steam port is eight square 

 inches, requiring the velocity of the steam in the blast pipe to be con- 

 siderably greater than in thecylinder. The average negative pressure 

 of the waste steam throughout the stroke is G lbs. per square inch 

 when running at the usual rate of 25 to •2s miles an hour ; and at greater 

 velocities the negative presstire has been found to increase to double 

 that amount and even more." 



From the first reason the evil it is intended to remedy by the lead of 

 the sliile appears to be, the tendency of the piston to become loose on 

 the piston rod, through tlie violent jerks caused by the motion of the 

 piston being changed .so very frequently as 5 times in a second. We 

 have to ascertain first, the immediate cause of the jerks, secondly, the 

 manner in which they occasion the piston to work loose, thirdly, their 

 force, and lastly, in what manner and to what extent this is diminished 

 by the lead of the slide. 



In order to accotmt for the production of these shocks or jerks, we 

 will consider what passes in the cylinder of a locomotive engine, and 

 first on the supposition that the steam acts on the piston with its full 

 pressure to the very end of the stroke, and that it is then shut off and 

 immediately begins to press with its full force on the other side of the 

 piston. 



On this head it is necessary to observe that, under tlie circumstances 

 here assumed, the steam could not, at the instant the piston commences 

 the stroke, press upon it with its full force (that is, with the same 

 force as in the middle of the stroke), on account of the necessity of 

 first filling the steam passage and waste space at the end of the cylin- 

 der. But, since the pressure of the steam remaining in these waste 

 spaces does not sensibly exceed that of the atmosphere, while the fresh 

 steam admitted into them has a very great excess of pressure, say 50 

 poimds on the square inch, the time required to fill them is certainly 

 very much less than that requited to fill one huntlredth part of the con- 

 tents of the cylinder, during which time the steam is pressing upon the 

 surface of the piston with a force increasing iVom the atmospheric 



12 



