Oct. 3, 1884.] 



♦ KNOWLEDGE ♦ 



277 



rose so unbidden to his ear, that he put it from him with 

 his hand, as if it were tangible." He can neither see nor 

 hear aught unusual ; yet he has "a strange idea that some- 

 thing unusual huug about the place." He strains his keen 

 ears and his hawk's eye.*. Nothing in the least unusual 

 was remotely shadowed forth." But he resolved that he 

 would come back early in the morning. 



In the morning he finds the watch, chain, and pin. In 

 a sense, his walk overnight was made memorable by tlie 

 morning's discovery. But was that all which made 

 the walk memorable 1 He mij^ht have found these 

 things without that night walk. I take it the walk 

 was memorable for other reasons. Jasper was there. 

 Probably Grewgious, too, was there, watching Jasper, when 

 Crisparkle had that strange sense of something unusual. 

 Jasper waited till Crisparkle had gone, and then, — under 

 the very eyes of Grewgious, — placed the watch and chain 

 anong the interstices of the timbers, and flung the shirt- 

 pin into the pool. If it could be proved that the watch 

 was kept unwound from Christmas night when it ran down 

 to midnight on the 27th, much would be made thereafter 

 o: the events of that memorable night. 

 {To be contitmcd.) 



THE INTERNATIONAL HEALTH 

 EXHIBITION. 



XVIII.— THE SOFTENING OF WATER— (conitnued). 



AMONGST the many processes that have been invented 

 to superinduce the condition through which hard 

 witer is fitted for manufacturing purposes there are a cer- 

 tain number still in general use which call for some notice 

 ill connection with the subject of these reviews, because 

 they are calculated to retard the progress which it has 

 been the aim of the modern inventor to substantiate. 

 Water ought to be preeminently soft to be of the greatest 

 value to the engineer, and when we recorded the results of 

 Mr. Porter's improvements on Dr. Clark's softening pro- 

 cess we intended to convey the notion that its utility lies in 

 the fact that it eliminates the causes of hardness in accom- 

 plishmg its results, and does not seek to do so by merely 

 correcting the evU influences of a pernicious supply. 



The ineflicient methods to which we have just alluded 

 iuay be classed together as auticrustation reagents, which 

 act in two ways — viz., either mechanically or chemically. 

 To the former group belong clay, sand, powdered glass, itc, 

 which are introduced directly into the boilers ; they are 

 there held in suspension by the ebullition of the water, and 

 are useful, inasmuch as they prevent the consolidation of 

 such salts as are apt to accumulate into a compact in- 

 crusting layer. They are to be discarded, because of 

 their tendency to add to the local heating of boiler- 

 plates, to waste of fuel, and to increased wear and tear of 

 the internal parts of the engine. These disadvantages are 

 but slightly modified in the employment of dissolving or 

 emulsifying solutions such as of potato-pealings, starch, 

 dextrine, ic. ; or of tannin-bearing compounds, particularly 

 of logwood, cashoo, sumach, tan, and chicory. Other re- 

 agents, which enforce a precii>itation of dissolved salts an 1 

 thereby prevent incrustation have also been used ; amongst 

 them are salts of baryta, caustic alkalies, and alkaline 

 carbonates, which are introduced at intervals or continu- 

 ously into the boilers along with the feed water. It is 

 true that tliey prevent incrustation, and by so doing enable 

 tlie boilers to be easily cleansed ; but insuperable objections 

 arise in the corrosion of taps, and the formation of soap 

 and priming. Innumerable patents have been taken from 



time to time, with a view to prevent the dangers arising 

 from the use of hard waters, but although some of them 

 are more valuable than others, they are all alike to be 

 condemned on the score of treating an evU, or rather of 

 permitting an evil which could be obviated. One of the 

 most recent and successful appliances used, however, deserves 

 mention on account of its novelty. It is known by the name 

 of Field's Electrical Scale Preventer, and, as its title 

 implies, the formation of adhesive crusts is prevented by 

 the precipitation and immediate removal of the causes of 

 hardness along currents induced by means of electricity. 



So serious in its results has the hardness of water been, 

 to engineers, that they have even resorted to the modifi.- 

 cation of their machinery ; to the superaddition of separate 

 depositing vessels, and to the employment of feed water- 

 heaters or economisers to relieve them. The only rational 

 system, however, which cannot by any possibility be open 

 to objection, ought to be looked for in a sufliciently 

 inexpensive process for the removal of the undesirable 

 impurities. 



Scarcely a year has passed since 1849 without the intro- 

 duction of some patent for the softening of water, and that 

 alone sutlices to prove the importance of the case. The 

 principal aims of such a process are efliciency and cheap- 

 ness, and that they have at length been attained is attested 

 to by the existence of the Porter-Clark, Atkins, Gaillet 

 and Huet, and Maignen's processes, all of which difi'er from 

 one another in the working out of details rather than in 

 essentials, and all of which are based on Professor Clark's 

 original researches, an excerpt of which we gave in our 

 last. 



An excellent condense of the Atkins, and Gaillet and 

 Huet processes* is given in Mr. Baldwin Latham's paper,t 

 read to the Society of Arts Water-Supply Conference, 

 recently held at the Exhibition ; and for the benefit of our 

 readers we shall conclude our remarks for the present by 

 quoting Mr. Latham's observations in their entirety. 



" The Atkins' Process is also a modification of the Clark 

 process, by which the space formerly required is reduced. 

 The lime is put into a vessel where lime-water is formed, 

 and this water is allowed to mix in its proper proportion 

 with the water to be softened in a specially-arranged mixing- 

 vessel, after which it passes into a reservoir of small dimen- 

 sions. From this reservoir it is conveyed to filtering vessels 

 which contain a special arrangement of filter, consisting of 

 a series of chambers mounted upon a central hollow shaft, 

 these disc-chambers being covered with prepared canvas, 

 upon which the deposit of chalk, ic, adheres, and through 

 which the softened water filters. These filters are cleaned 

 by means of revolving brushes. The apparatus does not 

 require power to maintain it while at work, the only power 

 used being that necessary to give motion to the brushes 

 when the apparatus is cleansed. The system may be seen 

 at work at the Henley-on-Thames Waterworks and at other 

 places." 



" The Process of Jlessrs. Gaillet and Huet. — In this pro- 

 cess, which was patented in February, 1883, the patentees 

 make use of certain known agents, the patent itself apply- 

 ing to the apparatus used for the purpose of producing the 

 results after the chemicals have been applied. The agents 

 they propose are lime and caustic soda. Whenever the 

 water contains organic matter, they use salt of alumina or 

 iron in addition. Iron, however, is not recommended in 



* A full account of which may be found in a small pamphlet 

 on "The Softening of Water," by Andrew Howatson, C.E., 11, 

 Queen Victoria-street, London, 18S4, being an extract from"fitnde 

 sur les Eaux Industrielles et leur Epuration," by Gaillet and Huet. 



t " Softening of Water," July 25, 1884, Health Exhibition Con- 

 ference. 



