Sept. 26, 1884.] 



♦ KNOWLEDGE . 



261 



Lime is made by burning ordinary limestone or chalk in 

 a kiln ; almost all the carbonic acid gaa is driven off and 

 lime remains behind. The process of burning cannot 

 always be fully completed, and individual cases are liable 

 to differ slightly from one another, so that only approxi- 

 mately pure lime is produced. Now this lime is soluble in 

 water, but, for the reasons just stated, it will not entirely 

 dissolve ; hence, in making the solution, it is advisable to 

 use a slight excess of lime. A solution thus prepared may 

 then be added to the hard water, when the carbonic acid of 

 the dissolved bicarbonate will react on the lime of the lime- 

 water, and leave the original bicarbonate of the hard water 

 in the form of an insoluble carbonate ; at the same time the 

 soluble lime of the lime-water takes up the liberated car- 

 bonic acid, and becomes also changed into an insoluble car- 

 bonate. Thus, two quantities, both of them insoluble, are 

 separated, and sink to the bottom of the vessel as a fine 

 white precipitate of mici-oscopical crystals of carbonate of 

 lime, leaving the water practically soft and fit for ordinary 

 use. The process has the great advantages of being ex- 

 tremely simple, adequately reliable, and comparatively 

 inexpensive. It has been estimated that a bushel of lime, 

 weighing about fifty-six pounds, and valued at 4^d., can 

 make four thousand gallons of very strong and clear lime- 

 watei', capable of softening about ten times that quantity 

 of hard water of the nature of the London district supply. 



That Clark's process is amply adequate to the supply of 

 a valuable water may be gathered from the following quo- 

 tation of results, which indicates the reduction in hardness 

 attained by its employment : — 



"The Porter-Clark Process," by J. H. Porter, 1884, p. 4. 



Cantorbury 26-3 to 4-9 



Caterham 21-2 „ 4-4 



Tring 26-3 „ 32 



The most serious objection to the process, however, is, 

 that when carried out on an extensive scale, the reservoirs 

 must be large and very costly. The precipitation of the 

 carbonate of lime, too, is, at most, extremely tardy in 

 action, and its accumulation in the tanks a most unde- 

 sirable item. All these drawbacks have been remedied in 

 the modified sy.stem known as the "Porter-Clark Pro- 

 cess," which is now being exhibited at South Kensington in 

 Stand 1,231, situated in a special building in the grounds, 

 outside the Western Gallery. An interesting pamphlet* 

 has been written upon the subject by Mr. Porter, in which 

 much valuable information is recorded. It is there shown 

 that the Poiter-Clark process provides for the treatment of 

 large quantities of water within a small area ; that the supply 

 can be regulated under continuous pressure at any desired 

 rate per hour, and that the filtering machinery used is so 

 constructed as to secure a purification of the filtrate, and 

 a prevention of subsequent contamination, through the 

 layer of precipitated carbonate of lime, which, in its turn, 

 can be easily removed. The chemical reaction, too, is 

 facilitated by the continuous agitation of the water with 

 the re-agent, and we may fairly congratulate the inventor 

 on having successfully overcome the many obstacles to the 

 effectual working of a system of water purification which 

 needs but to be known to be highly appreciated and 

 generally adopted. 



We hear that it is proposed to publish by subscription the 

 " Vital Statistics of the late Dr. William Farr " in an octavo volume 

 of some 450 pages. All interested in this very important post- 

 humous work of our famous English statistician should communi- 

 cate with Mr. E. White Wallis, the Secretary of the Sanitary 

 Institute of Great Britain, 74a, Margaret-street, Regent-street, W. 



* " The Softening and Purification of Hard Waters," by John 

 Henderson Porter, A.I.C.E., 1, Tudor-street, London, E.G., 1884. 



editorial (gossip. 



■■I 



In no way can the amateur astronomer do a more imme- 

 diate public service than by supplying correct time to a 

 district far from a post-oftice to which it is flashed by tele- 

 graph ; and possessors of small transit instruments may 

 pick up a profitable "wrinkle " or two in connection with 

 this from the perusal of an article on taking time observa- 

 tions in the current number of that capital little American 

 serial, the Sidereal Messenger. 



And while mentioning the Sidereal Messenger, the 

 number of which I have just spoken also contains an 

 account of a remarkable apparition on the evening of July 

 30, ult., of a narrow, thin, white cloud, like a comet's tail, 

 which seems to have crossed the sky in a somewhat similar 

 manner to (though not in the same direction as) the strange 

 fusiform magnetic or auroral cloud observed in England by 

 Mr. Rand Capron and others, on Nov. 17, 1882. It was 

 seen at Atlantic City, New Jersey. 



Believers in the influence of sun-spots on the weather 

 may note that while we have enjoyed great and exceptional 

 heat here during the present summer, it has been one of 

 the coldest known for many years in Constantinople, 

 where the mean temperature for July and August has- 

 actually been three degrees below the average. Presumably 

 they have the same sun in Turkey that we have in England. 

 There have further been some splendid spots and groups of 

 spots on the sun's face during the past few weeks, although 

 the (official) period of maximum has passed. 



The strange and beautiful sunsets, or rather " after- 

 glows," still continue. In connection with the persistence 

 of this phenomenon it is noteworthy that on the very clearest 

 days a strange kind of haze still surrounds the sun ; in fact, 

 while in the oi)posite quarter of the heavens the sky is of 

 the most vivid cerulean blue, for many degrees around the 

 sun is a very faint, but semi-opaque, veil, which becomes at 

 once visible on hiding the sun with the hand and regarding 

 the neighbouring region. A valued friend and correspon- 

 dent of great eminence in the scientific world suggests the 

 question whether this " mutton broth " (as he calls it) is really 

 atmospheric at all, in fact, whether it may not be cosmical 

 and a true appendage of the sun 1 If so, yet another 

 explanation would seem to be possible of our wondrous 

 evening skies than that afforded by Krakatoa dust. 



Many people fondly hoped that the discovery by Dr. 

 Koch that the " comma bacillus " was invariably presen 

 in (and was, in fact, the active agent in the production of) 

 cholera, had brought us in sight of the means of combating 

 that ghastly scourge. Unfortunately, Surgeon-Major 

 Lewis, of the Army Medical School at Netley, who has 

 been investigating this question at Marseilles, has come to 

 the conclusion that the " comma " is neither more nor less 

 injurious than any other microbe ; so that we are landed 

 very much where we were before the commencement of 

 Dr. Koch's researches. 



Vaccination' ix the Arjts' axi> Navy. — A return, showing the 

 efficacy of vaccination, has been issued, entitled " Small-pox (Army 

 and Navy)." In 1882 the annual strength of the army was 174,557, 

 and the number of deaths from small-pox was five, or in the ratio 

 of 03 per 1,000. The number of men entering the service that 

 year was 26,129. In the navy a similar excellent result was notice- 

 able. In 1882 the mean strength was 57,067 ; the number of deaths 

 two, or a proportion of O'S per 1,000; and 0,998 men entered in the 

 year. As every man who enters her Majesty's services is compelled 

 to submit to vaccination, these figures, if submitted to persons of 

 ordinary intelligence, and not to rabid anti-vaccinators, wonld be 

 absolutely convincing. — iledical Press and Circular. 



