June 11, 1876] 



NATURE 



177 



in terms, the machine was ever put to work, although it is said 

 that M. Amonton made many experiments to convince the Aca- 

 demy of the practicability of his invention. M. Amonton pro- 

 posed to have a metallic wheel revolving on a horizontal axis ; the 

 outer rim of the wheel was to be divided into a number of sepa- 

 rate air cells, each of which had a channel so as to communicate 

 with other cells, water-cells, arranged round the wheel nearer to 

 the centre than the air-cells ; the air-cells as they passed over a 

 fire were to be heated, and the air was to drive this water up to 

 one side of the wheel, so as to keep that side always loaded, 

 and thus give the wheel a tendency to revolve. The cells after 

 Uaving the neighbourhood of the fire were to be cooled by passing 

 through water to re-contract the air ready for the next operation. 



No. 1,940, which is before me, is a model of Stirling's hot-air 

 engine, but time does not remain to describe it. 



Besides hot-air engines, we have had engines working by the 

 explosion of gunpowder, and others working by the explosion of 

 gases. No. 1,945 is Langen and Crossley's gas engine, from 

 which I believe extremely excellent results have been obtained. 



I will now ask you to look at a tabular statement which shews 

 the consumption of fuel in some agricultural engines, when 

 un 'er trial, expressed in pounds per horse-power per hour, and 

 also in millions of pounds raised one foot high by the consump- 

 tion of icwt. of coals. I told you how excellent were the results 

 at which our agricultural engineers had arrived ; you will see that 

 one of those machines, working with 8olbs. steam, and of course 

 without condensation, has developed, not a gross indicated horse- 

 power, but an actual dynamometrical horse-power, for 2 79lbs. 

 of coal per horse per hour, giving a duty of as much as 79^ 

 millions. This high result was obtained by the excellence of 

 the boiler and of the combustion, as well as by that of the engine. 

 If you look at the column of evaporation you will find that as 

 much as 1 1 'Stlbs. of water were converted from the temperature 

 of the boiling point into steam by the combustion of lib. of 

 coal ; this was due, not to tlie merits of the boiler alone, but 

 to tho extraordinary ability of the stoker, and to the care and 

 Iftbour bestowed, a care and labour far too expensive to be em- 

 ployed in practice. But should not we engineers endeavour to 

 ascertain whether we cannot by mechanical means, practically, 

 vdth ceitainly and cheapness, procure an accuracy of combus- 

 tion as great, or even greater than that which can be got by the 

 almost superhuman attention of a highly-trained man, who at 

 the end of four hours of such work is utterly exhausted ? Many 

 forms of fire-feeders have been attempted and used with more 

 or less success, but I cannot help thinking that in order to obtain 

 the accurate proportioning of air and fuel, by which alone we can 

 get efficient and economical combustion, we shall have to turn 

 our attention in the direction of dealing with the fuel in a com- 

 minuted state, either by converting it into gas, as is done by our 

 president. Dr. Siemens, by availing ourselves of liquid fuel, or 

 by employing the process of Mr. Crampton, and making the 

 fuel into an impalpable powder, that may be driven into the 

 furnace by the air which is there to consume it. 



By these, and by other means, we may hope to improve com- 

 bustion. By strict attention to the proportioning of the parts of 

 the boiler we may hope to make the best use of this improved 

 combustion. By higher initial pressure, by greatt r expansion, and 

 by the general employment of condensation, wherever prac- 

 ticable (and by the use of the evaporative condenser there are 

 very few cases in which it is not practicable), we may trust that 

 the steam-engine, even on its present principle, will be rendered 

 more economical than it has ever yet been, and may give us 

 more th-m that one-eighth or one-ninth of the total force residing 

 in the luel which now alone we get under the very best and 

 most exceptional conditions. A large loss, however, must with 

 steam-engines, as we now know them, always be incurred. We 

 cannot hope to deal vnth initial pressures and temperatures cor- 

 responding with steam of a density equal to that of water, nor to 

 carry expansion down to the point where ice would be formed 

 in the condenser. But wonderful as the steam-engine is, worthy 

 as it was and is of Belidor's eulogium (which I read to you), we 

 know it is not the only heat motor, and we are aware that there 

 are other forms of such motors which, theoretically at all events, 

 promise higher results. 



By improvements in the existing steam-engine, by the inven- 

 tion and development of other heat motors, by the employment 

 of the power of water and of wind, either as principal motors or 

 as auxiliaries, we may look to further progress in the machines— 

 the subject of my address—" Prime Movers." 



I have brought before you, of necessity hastily, and therefore 

 (and also on account of my own incapacity for the task) imper- 



fectly, the leading improvements which have been made in prime 

 movers from the date of the water-wheels of Vitruvius to the 

 best-devised steam-engines of our own day. These improve- 

 ments have been effected by men like Papin, Savery, Newco- 

 men. Watt, Symington, Stephenson, and others, who were not 

 mere makers of engines, but were men full of an ardent love of 

 their noble profession, who followed it because of the irresistible 

 attraction it possessed for them ; followed it from their boyhood 

 to their grave, and in that very following found their great 

 reward. These men undoubtedly possessed that combination of 

 science and practice, which combination, Dr. Tyndall has told us, 

 is necessary if either science or practice is to continue to live ; 

 for, to use his expressive language, without this combination 

 they both die — die of atrophy ; the one becomes a ghost, the 

 other a corpse. 



We have every reason to believe that this combination will 

 rapidly become even more fully developed, not onlyin the engineers 

 of the present day, but in those of the next and of succeeding 

 generations, and to such men as these we may trustfully leave the 

 continued improvements of prime movers, resting content with 

 the knowledge that a more general application of these ma- 

 chines must of necessity follow such improvements, and that 

 the day will soon dawn when in no civilised country will there 

 continue to be the temptation to employ intelligent humanity in 

 the brutal labour of the turnspit, or of the criminal on the 

 treadwheel. 



OCEAN CIRCULATION'^ 



'X*IIE present theories with regard to ocean circulation do not 

 appear to account for many of the phenomena with which 

 we are acquainted ; and my object in this paper is to state very 

 briefly my own opinions, with a view to provoking discussion, 

 and, in this way, to forward the knowledge of a very difficult 

 but interesting subject. I believe that there are at the present 

 moment two rival doctrines, viz. : — 



1. One which attributes all currents to the influence of the 

 winds. 



2. Another which attributes all ocean currents to gravitation. 

 I entirely disagree with the first doctrine, and shall address 



my remarks to the second. I quite think that ocean circulation 

 is the result of gravitation, but, contrary to what I believ« to be 

 the present opinion, I hold that the cold feeding streams flow in 

 a wave from the surface of the Polar oceans, and not from the 

 bottom. 



The points that I wish particularly to suggest for consideration 

 are as iollows : — 



I. That all octan currents run from a higher to a lower level. 



2.^ That the upward pressure produced in the equatorial 

 regions by the constant inflow, at the bottom, of water from the 

 Polar regions owing its high specific gravity to its contr action 

 from cold ; and, vice versA, the constant inflow at the bottom of 

 the Polar regions, of water flowing from the equatorial regions 

 and owing its high specific gravity to its salinity, must, these 

 streams flowing Irom a higher to a lower level, tend to elevate 

 the lighter surface-water and drift it down a slightly inclined 

 plane as a surface-current. 



3. That the primary cause of the origin of all ocean currents 

 is the change in the specific gravity of sea-water from one of the 

 following causes, viz. : 



(rt) Evaporation ; the vapour arising from the surface bein^ 

 fresh, and leaving its saline constituents behind it. 



(b) The excess of precipitation over evaporation, particularly 

 in the Polar sea?, which by admixture with the surface-water 

 increases its freshness. 



(c) The expansion of surface-water through heat. 

 ((/) The contraction of sea-water through cold. 



It is generally admitted that currents of both air and water 

 flowing from the equator to the poles having an excess of easterly 

 momentum due to the velocity of rotation of the earth's surface 

 in low latitudes as compared with the lejser velocity in high 

 latitudes, 3 must outstrip the earth's motion, and consequenUy 



' More particularly with reference to the North Atlantic Ocean, being an 

 abstract of a paper read to the Caterham Literary Society in March last. 



s 1 hold it to be impossible that you can have any such thing as an ocean 

 level unless the different strata or layers of water from the equator to the 

 poles are not only isometrical and isotherm.il, but are also of equal specific 

 gravity ; whereas the known ranges of variation of both temperature, salinity, 

 and depth of different strata of sea-water vary much in different places and 

 indifferent oceans. There is a constant disturbance of equilibrium, and the 

 constant effort to restore and equalise it produces the currents. 



3 The rotatory velocity of the earth's surface being about 1,440 feet per 

 second at the equator, 720 feet per second in 60° of latitude, and decreasing 

 to zero at the poles. 



