216 



SCIENCE. 



[Vol. YL, No. 136. 



appeared that the ocean-bed at that coast is a shift- 

 ing quick-sand, and some doubt prevailed as to the 

 practicability of such a structure at any reasonable 

 cost. 



Prof. E. H. Thurston's paper on cylinder condensa- 

 tion was of great scientific and practical value. The 

 fact, the manner, and the effect of condensation in 

 steam-cylinders, were made clear, even to those but 

 little acquainted with the subject. Nearly all the 

 losses met with in steam-engines are due to this 

 cause. Watt found that three-fourths of the steam 

 used in his engine was lost by condensation. In or- 

 dinary engines of modern construction, about twenty- 

 five per cent is the usual loss ; while in some large 

 engines this loss has been reduced to ten or fifteen 

 per cent. This waste depends upon the temperature 

 of the surface of the cylinder when the steam enters, 

 the temperature of this surface when the steam is 

 exhausted, the extent of surface exposed, and the 

 time of a revolution of the engine. These four varia- 

 ble elements bear different relations to each other in 

 different engines operating under unlike conditions. 

 The engineer has at present no means of designing 

 an engine for given conditions for which he can 

 calculate just what will be the waste, due to con- 

 densation from these causes. The complete solution 

 of the problem requires that experiments be made, 

 first, to ascertain the variation of loss due to a change 

 of one of these quantities, all the others remaining 

 constant, and that the law of such variation be 

 mathematically expressed. A second of these varia- 

 bles is r eated in the same manner; and so on until 

 the law of variation of loss, due to change in each 

 one of these variables, has been expressed. Then, if 

 it be possible to combine all these results into a 

 single formula, this formula will express the com- 

 plete theory, and give the full solution of the prob- 

 lem. These experiments were made with a Harris- 

 Corliss engine, capable of developing over five hun- 

 dred horse-power. The engine was controlled by a 

 large brake constructed for this purpose. Curves 

 were plotted, representing the results of the different 

 series of experiments recorded. While the full solu- 

 tion of the problem imdertaken may involve the ne- 

 cessity of further experiments, the results tabulated 

 in this paper will prove of great value to engineers. 

 The paper will soon be in print. 



A description of the large Prony-brake used in the 

 experiments just referred to, formed the subject of a 

 short paper by the same author. The size of this 

 brake, and the extraordinary requirements made upon 

 it, viz., that of transforming five-hundred horse- 

 power of mechanical energy into heat, and giving up 

 this heat with sufficient rapidity to prevent the undue 

 heating of the machine, were the principal features 

 of the device. 



The discussion on the best methods of teaching 

 mechanical engineering was opened by the report 

 of a committee, through Prof. J. B. Webb its 

 chairman, who alluded to the discussion of the 

 same subject by the Society of mechanical engi- 

 neers at Atlantic City. That discussion showed 

 that engineers desire that technical schools shall 



give thorough preparation in theory and princi- 

 ples; and, also, that they insist upon the impor- 

 tance of such practical knowledge and skill — in all 

 who are to direct men, and plan and execute work 

 — as will enable the foreman or engineer to instruct, 

 direct, and, if necessary, show his men how to do 

 their work. 



Prof. K. H. Thurston said that the training should 

 be adapted to the work to be done. Therefore 

 he favored classification into manual training-schools, 

 schools of mechanic arts, and schools of engineering. 

 A large proportion of the students who start at the 

 beginning of the course will prove fitted to become 

 workmen only, and may go from the manual train- 

 ing-school into a special course for some particular 

 trade, or into the shop. Of the remainder, some will 

 be able to do construction and simple designing, and 

 might go from the school of mechanical arts into a 

 special course preparing them for superintendents 

 and directors of workmen. A few will have ability 

 to become engineers; and should have, not only 

 manual training and the mechanic arts, but, in addi- 

 tion, an unusually good knowledge of mathematics, 

 applied mechanics, physics, including electricity, and 

 some chemistry. Mechanical engineering requires a 

 better knowledge of the physical sciences than any 

 other profession. The higher a man goes, the better 

 must be his knowledge of the use of tools. Teachers 

 of engineering should be men who have had good 

 training through a broad practical experience in 

 the solution of engineering problems, and should 

 have retained their theoretical knowledge by read- 

 ing and study. Such men, at present, are rarely 

 found. 



Further discussion brought out the suggestions, 

 that there are no manual training-schools where a 

 boy can learn a trade before entering the higher 

 schools; that the St. Louis and Chicago manual 

 training-schools will not make workmen, and that 

 probably not five per cent of their students will ever 

 become workmen. These schools are appendices to 

 the public schools, to give a general training by a 

 different method. Technical schools try to crowd 

 too much into four years. Principles should be 

 taught upon which the man can build for himself. 

 Men must know how to think, and they will be able 

 to learn engineering. Practice is theory embodied ; 

 and, in so far as practical experience or work can aid 

 theory, the two should be intimately mixed or 

 blended from first to last. Manual training aids 

 the judgment. Shop-work, interspersed with classi- 

 cal studies, would not diminish proficiency, and 

 would add a valuable element. Shop-work at Mich- 

 igan university is offered to all students, and is often 

 elected by others than those studying engineering. 

 Actual shop-work, too, is an efficient ' conceit killer.' 

 More liberal preparation should be required for ad- 

 mission to technical schools. The important feature 

 of the discussion was the advocacy of courses of 

 study, leading one into the other, with natural stop- 

 ping-places, each of which is a starting-point for 

 some special trade, position or profession, adapted 

 to the talent and ability of the individual student. 



