June 7, 1889.] 



SCIENCE. 



433 



This subject is so little (generally) understood, that it seems ne- 

 cessary to use the above illustration for the benefit of the casual 

 reader, although to the chemist a hundred different applications of 

 the same law will suggest themselves. Indeed, it is noted here for 

 the purpose of calling more emphatic attention to the simple fact 

 that water may contain impurities in absolute (chemical) solution, 

 and that such impurities, by the addition of another substance, may 

 be rendered tangible, and capable of withdrawal from the water by 

 purely mechanical means. 



Equally clear and understood should be the statement that 

 water may contain impurities in a state of fine (mechanical) sus- 

 pension, — so fine that they would flow wherever water would 

 flow, — and these, by the addition of another substance to the 

 water, be made to flock together into groups, a thousand or two 

 into one (as clouds are condensed into drops) ; and that one, with 

 its fellows, be tangible, and easily removed from the water by 

 purely mechanical means. 



It follows, that if the earth contains in abundance this " sub- 

 stance," which has the dual property of disengaging matter held in 

 solution, and rendering the same tangible, and also of curdling to- 

 gether matter held in so fine a state of division as to almost elude 

 the senses into a state of perfect tangibility, we at once get at the 

 secret of how nature makes the true spring-water, so wonderfully 

 pure and sweet to the taste, as well as brilliantly clear, and inviting 

 to the eye. 



What is this substance or substances.' Usually some combina- 

 tion of lime, iron, potassium, aluminum, etc., with other bases, such 

 as sulphur or carbon, — all existing naturally in the great mother 

 matrix, the earth. 



The almost universal diffusion of the aluminiferous earth (red 

 clay) makes that substance take a more prominent place among 

 the agents above alluded to. Water cannot flow far in any part of 

 the world without encountering in its course the coagulating or 

 curdling effect of this single element. Some of these clays are 

 more heavily charged or freighted with aluminous compounds than 

 others. Waters fouled by such are more quickly subsided. In 

 this fact we have a clew to the explanation of why it is, that, of 

 two different waters showing the same degree of turbidity from 

 clayey impurities, such impurities will subside quickly in one, while 

 in the other they may not subside in months. As proof that the 

 quick subsidence is due to the presence of these salts, we have 

 only to add a minute proportion of such (usually aluminum sul- 

 phate) to the other water to' produce the same effect. Hence, 

 when water issues from the earth in a very clear and perfect state, 

 we may always be sure that it has encountered somewhere on its 

 travels a body of earth or mineral containing a suitable coagulant, 

 the action of which coagulant upon the water accounts for its won- 

 derful purity aside from and entirely independent of the mere filter- 

 ing effect of the earth. 



It has remained for the present decade to apply the above knowl- 

 edge to the art of filtration of water, and for the first time produce 

 results equal to nature. 



As this industry extends, it will become a common thing to see 

 " spring " water issue from our city faucets, as is already the case 

 in a few American cities, notably Atlanta, Long Branch, and New- 

 port. 



The study of this subject furnishes a striking example of Na- 

 ture's exhibiting, in the humble wayside " spring," the results of 

 her perfect handiwork for the observation and admiration of man 

 throughout all ages and countries, only to deliver up her secret to 

 the pale student of this century of science. 



John A. C.-^ldwell. 



THE USE OF SPIRIT AS AN AGENT IN PRIME 

 MOVERS. 



A PAPER on the above subject was prepared by A. F. Yarrow 

 at the request of the Council of the London Society of Arts, and 

 was presented May 22. It did not treat of the adoption of 

 spirit or liquid hydrocarbons, such as petroleum, when used as a 

 substitute for coal as fuel, which is an entirely distinct subject, but 

 with the use of volatile liquids in lieu of water, to produce power, 

 when converted by heat from the liquid to the vapor state, in the 



same way that power is obtained from the conversion of water into 

 steam. 



In the year 1856 this subject attracted much attention in France ; 

 and, as a matter of fact, several large steamers were built, and 

 ran between Marseilles and Algiers, in which ether was evaporated 

 in combination with steam for working the propelling machinery. 

 The engines were on the Du Tremblay system. The steam, after 

 having performed work in one cylinder, instead of going at once to 

 the condenser, was used to evaporate ether in a tubular evapora- 

 tor, by which means a portion of the remaining heat in the steam 

 was absorbed instead of being wasted. The ether vapor so pro- 

 duced was used in another cylinder, the additional power thus ob- 

 tained being a clear gain. These steamers ran, making regular 

 voyages, for some years, but were ultimately abandoned. 



The gain obtained is clearly due to the ether taking a portion of 

 the heat of the exhaust steam, and turning it to useful account, 

 which would otherwise be wasted in raising the temperature of the 

 condensing-water. The ether used evaporates at about 104° F. : it 

 will therefore be seen to what a low temperature the steam or 

 water can be brought down, and still be useful in evaporating the 

 ether. 



The system was no doubt enconomical as regards fuel ; but the 

 ether was so difficult to keep, that a renewal of about one gallon 

 per hour was required to make good the leakages. There was also 

 serious risk of explosion on account of these leakages, because the 

 ether, when free, rapidly vaporizes, and when in this state is ex- 

 plosive if mixed with the atmosphere. The difficulties which at 

 that time had to be dealt with are, however, now greatly reduced. 

 Ether, being the spirit used, was far more costly than other volatile 

 liquids which are available now, and consequently any leakage then 

 represented an important item in the working expenses ; also, at 

 that period, means for obtaining good workmanship were not avail- 

 able to the engineer, as they are at present, accuracy of workman- 

 ship, and soundness of materials, being essential points in dealing 

 with the vapor of these volatile liquids, as it penetrates joints and 

 castings which no steam would. In fact, an amount of care is 

 necessary beyond what is needed in the best steam-engine practice, 

 and sufficiently good work was not available thirty-two years ago. 



The success of some small boats lately built in the United States, 

 propelled by spirit vapor, induced Mr. Yarrow to take the matter 

 up with a view to investigate it, and see whether the results would 

 justify his going fully into the matter with a view to its further de- 

 velopment. These preliminary investigations look promising. 



The apparatus with which the experiments were tried was a 

 small steam-engine of ordinary construction, which actuates a shaft 

 and fly-wheel in the usual way. There was a brake attached to 

 the shaft, with a spring balance and index ; also a revolution 

 counter, so that he was enabled to obtain the actual power de- 

 veloped. There was also fitted to this little engine an ordinary 

 indicator, from which to obtain diagrams. 



The steam-boiler had no special feature about it : it had simply a 

 combustion-chamber and a straight flue through to the funnel. 

 There was; no attempt at economy of fuel, because there was no 

 object in so designing it, all he wished to obtain being the com- 

 parative results on a common basis. The heat was obtained by 

 means of ordinary gas, burnt in a large Bunsen burner. Gas was 

 selected as the means of heating because the exact quantity could be 

 accurately regulated and recorded, and with this view there was 

 attached to the inlet pipe a gas-meter. The exhaust from the 

 cylinder passed out, and terminated in a coil of pipe immersed in 

 a tank of running water for the purpose of condensing the steam. 

 From there the condensed steam ran into a hot-well, and passed 

 on to the feed-pump on the engine, and was forced back into the 

 boiler, so that an entire circuit was made. This completes the ar- 

 rangement for working the engine by steam. 



For the corresponding system, when spirit vapor was used, in- 

 side the upper part of the boiler was a copper coil, the inlet to 

 which was at the side, and the outlet at the top, whence it passed 

 to the engine. The exhaust pipe from the cylinder was led in this 

 case into a tank where the vapor was condensed, and passed on to 

 the hot-well, thence to the pump, and was forced back into the coil 

 inside the boiler, thus making this circuit complete. Two sets of 

 pipes, condensing-coils, etc., were adopted, so as to avoid, as far as 



