6o 



NA TURE 



yNov. 15, 1883 



bottom, with a layer of felspar separating the two. A 

 current of water sweeps tlirough the whole, and is drawn 

 off partly at the top, carrying with it the stone, and partly 

 at the bottom, carrying with it the fine coal. 



The above are instances where science has come to 

 the aid of engineering. Here is one in which the obli- 

 gation is reversed. The rapid stopping of railway trains, 

 when necessary, by means of brakes, is a problem which 

 has long occupied the attention of many engineers ; and 

 the mechanical solutions offered have been correspond- 

 ingly numerous. Some of these depend on the action of 

 steam, some of a vacuum, some of compressed air, some 

 of pressure-water; others again ingeniously utilise the 

 momentum of the wheels themselves. But for a long 

 time no effort was made by any of these inventors tho- 

 roughly to master the theoretical conditions of the problem 

 before them. At last, one of the most ingenious and 

 successful among them, Mr. George Westinghouse, re- 

 solved to make experiments on the subject, and was 

 fortunate enough to associate with himself Capt. Douglas 

 Galton. Their experiments, carried on with rare energy 

 and perseverance, and at great expense, not only brought 

 into the clearest light the physical conditions of the ques- 

 tion (conditions which were shown to be in strict accord- 

 ance with theory), but also disclosed the interesting 

 scientific fact that the friction between solid bodies at 

 high velocities is not constant, as the experiments of 

 Morin had been supposed to imply, but diminishes rapidly 

 as the speed increases— a fact which other observations 

 serve to confirm. 



The old scientific principle known as the hydrostatic 

 paradox, according to which a pressure applied at any 

 point of an inclosed mass of liquid is transmitted un- 

 altered to every other point, has been singularly fruitful 

 in practical applications. Mr. Bramah was perhaps the 

 first to recognise its value and importance. He applied 

 it to the well known Bramah press, and in various other 

 directions, some of which were less successful. C)ne of 

 these was a hydraulic lift, which Mr. Bramah proposed 

 to construct by meins of several cylinders sliding within 

 each other after the manner of the tubes of a telescope. 

 His specification of this invention sufficiently expresses 

 his opinion of its value, for it concludes as 'follows :— 

 "This patent does not only differ in its nature and in its 

 bo\mdless extent of claims to novelty, but also in its 

 claims to merit and superior utility compared with any other 

 patent ever brought before or sanctioned by the legislative 

 authority of any nation." The telescope lift has not come 

 into practical use; but lifts worked on the hydraulic prin- 

 ciple are becoming more and more common every day. 

 The same principle has been applied by the genius of 

 Sir William Armstrong and o'hers to the working of 

 cranes and other machines for the lifting of weights, &c. ; 

 and under the form of the accumulator, with its dis- 

 tributing pipes and hydraulic engines, it provides a store 

 of power always ready for application at any required 

 point in a large system, yet costing practicallv nothing 

 when not actually at work. This system of high-pressure 

 mains worked from a central accumulator has been for 

 some years in existence at Hull, as a means of supplying 

 power commercially for all the purposes needed in a large 

 town, and it is at this moment bein-j carried out on a 

 wider scale in the East End of London. 



Taking advantage of this system, and combining with 

 it another scientific principle of wide applicability, Mr. 

 J. H. Greathead has brought out an instrument called the 

 "injector hydrant," which seems likely to play an impor- 

 tant part in the extinguishing of fires. This second prin- 

 ciple is that of the lateral induction of fluids, and may be 

 thus expressed in the words of the late William Froude :— 

 " Any surface which in passing through a fluid experi- 

 ences resistance must in so doing impress on the particles 

 which resist it a force in the line of motion equal to the 

 resistance." If then these particles are themselves part 



of a fluid, it "will result that they will follow the direc- 

 tion of the moving fluid and be partly carried along with 

 it. As applied in the inje tor hydrant, a small quantity 

 of water derived from the hi jh-pressure mains is made to 

 pass from one pipe into another, coaling in contact at 

 the same time with a reservoir of water at ordinary pres- 

 sure. The result is that the water from the reservoir is 

 drawn into the second pipe through a trumpet-shaped 

 nozzle, and may be made to issue as a stream to a con- 

 siderable height. Thus the small quantity of pressure- 

 water, which, if used by itself, would perhaps rise to a 

 height of 500 feet, is made to carry with it a much larger 

 quantity to a much smaller height, say that of an ordinary 

 house. 



The above are only a few of the many instances which 

 might be given to prove the general truth of the fact with 

 which we started, namely, the close and reciprocal connec- 

 tion between physical science and mechanical engineering, 

 taking both in their widest sense. It may possibly be 

 worth while to return again to the subject, as other illus- 

 trations arise. Tno such have appeared even at the 

 moment of writing, and though their practical success is 

 not yet assured, it may be worth while to cite them. The 

 first is an application of the old principle of the siphon 

 to the purifying of sewage. Into a tank containing the 

 sewage dips a siphon pipe some thirty feet high, of 

 which the shorter leg is many times larger than the 

 longer. When this is started, the water rises slowly and 

 steadily in the shorter column, and before it reaches 

 the top has left behind it all or almost all of the 

 solid particles which it previously held in suspension. 

 These fall slowly back through the column and collect at 

 the bottom of the tank, to be cleared out when needful. 

 The effluent water is not of course chemically pure, but 

 sufficiently so to be turned into any ordinaiy stream. The 

 second invention rests on a curious fact in chemistry, 

 namely, that caustic soda or potash will absorb steam, 

 forming a compound which has a much higher tempera- 

 ture than the steam absorbed. If, therefore, exhaust 

 steam be discharged into the bottom of a vessel contain- 

 ing caustic alkali, not only will it become condensed, but 

 this condensation will raise the temperature of the mass 

 so high that it may be employed in the generation of fresh 

 steam. It is needless to observe how important will be 

 the bearing of this invention upon the working of steam- 

 engines for many purposes, if only it can be established 

 as a practical success. And if it is so established there 

 can be no doubt that the experience thus acquired will 

 reveal new and valuable facts with regard to the con- 

 ditions of chemical combination and absorption, in the 

 elements thus brought together. 



Walter R. Browne 



THE LITERATURE OF THE FISHERIES 

 EXHIBITION^ 

 II. 

 'pHE depopulation of our littoral fisheries is the 

 ^ text of a paper on " Crustacea,'' by Mr. T. Cornish, 

 who proposes to meet the difficulty by establishing a 

 market for " middle-sized " Crustacea (and even fishes), 

 other than those which we now eat, either as "luxuries 

 or dainties." There is an amusing but authoritative air 

 of originality about this paper. Mr. W. S. Kent, on the 

 other hand, proposes the "Artificial Culture of Lobsters'' 

 as a remedy for the same evil, and recounts some inter- 

 esting experiments made by himself — on a small scale — 

 in which he succeeded in rearing the young lobsters 

 taken captive. The leading developmental phases are 

 set down for the guidance of others, but the account 

 given is deficient in record of the earlier stages of the 

 process. This is important, as the writer (presupposing 



^ Concluded from p. 36. 



