♦ KNOWLEDGE 



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All Semittamcea, Ckecuts, and Poft-OMc* Order* 



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'k* Editor w^ll be Xumbered. For convenience of refer 

 r^erring to ang Utter, Ktii oblige by Mentioning it* nn 



Ati Letter* or Querie* to the Editor tchieh require attention in the current i»»ue oj 

 :50iri.iDGB, thonld reock tht Futlishing OJice not Uter tkan the Saturday preceding 

 i* daif ^publication. _ 



mnst be concise; they must be drawn 



that Ihev may ro untouched »o the 



Qununi cations, therefore, as well as' queries, or repHes to 



ppear as such) should be written on $i»par»te leaves. 



(either because too iong, or unBuitable, or dealing with 



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ther be briefly referred to in answersto correspondents, or acknowledged 



reeerred (or the purpose. 



lan only ti to be contemned and de(:pi«ed who ie not in t 

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 Farad ajf. 



■pa niistalte^ but preat harm 



pnotert ; private 

 queries (iiktended 

 (II.) Letters which 



"In knowledge, th 

 state of tr«ni«ition. 

 than fixity of opinion 



•'There is no harm ^ „ ^., 



me a man who make* no miatakee, and I will 

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•* God's Orthodoxy is Truth."— CSar/« Kingsley. 



0vix Corrrsponbnuf Columns. 



MACAn.AY (IN SMAI.L-roX. 



[414] — As an addciidnm to what Macaulay says (as quoted in jour 

 edition of Saturday last), in respect of the'prevalence of small-pox 

 2(0 years afc'o, permit me to call your attention to his opinion as to 

 the value of vaccination as a preventive. 



" In spite of these elotiucnt eulogies (on the introduction of 

 Hcming's lamps for the purpose of lighting the streets of London) 

 the cause of darkness was not left undefended. There were fools 

 in that af,'o who opposed the introduction of what was called the 

 new li^rht, as strenuously as fools in our age have opposed the intro- 

 duction of vaccination and railroads ; us strenuously as the fools of 

 an npe anterior to the dawn of history doubtless opposed the intro- 

 duction of the plough and of alphabetical writing." 



As showing the intensity and prevalence of the disease at that 

 time, I may parenthetically mention that three of the leading 

 characters of that reign Buffered most severely, viz., William, Mary, 

 and Bcntinck ; Mary dying of it. 



Direct and positive evidence of the terrible nature of a visitation 

 of small-pox on a population entirely (or nearly so) unprotected by 

 vaccination, is afforded by the accounts which reach us of the out- 

 break now raging in the Island of Hayti (reported in the Jiriliah 

 ilt'lical Journal a week or two since), "when the nnmber of deaths 

 during this single outbreak, and amongst a sparse population, is 

 calculated at no less than 20,000 victims. Obsekver. 



A MISPLACED SPA. 



[415] — Most people must have noticed that new brick buildings 

 are often defaced by a white incrustation which disappears in damp 

 weather and reappears in sunshine, and often obstinately continues 

 to do so, on parts of buildings sheltered from rain, even after the 

 structure is no longer new. An example may be seen in a hand- 

 some Wesleyan church in the Anerley-road, near Anerley station, 

 and in new houses and walls about Red Hill, and at Thornton 

 Heath, near Bcnlah Spa; and in what other localities is a question 

 dewrving investigation. 



f)n asking the cause of this from workmen, foremen, bnilders, 

 and even from a local architect, I have received the various answers 

 that it was lime, saltpetre, and that sea salt had been used in the 

 mortar ; only yesterday, I was told confidently, " that, sir. is the 

 chalk drying out." It is curious that so remediable an nnslghtlinesa 

 has not been letter examined by these experts, for it is Glauber's 

 salt, an>l therefore easily removable. 



At the ffKit of the Surrey Highlands, where the Dorking and 

 Rcigatc sand begins, east of Kcigate, to diverge from the chalk, and 



to give place, between it and the chalk, to n ba.sin of blue clay, and 

 in the cellar of a house which I inhabited at tiatton I'oint, I found 

 esuiliiig from a wall built against the clay, crops of long feathery 

 crystals, which I thought at first were some kind of vegetable 

 mould. These constantly reappearing, I gathered in a gallipot, 

 li.\iviated, strained, and found to be jiurc sulphate of soda. I have 

 no doubt the deposit continues still. 



People there sometimes complained that the well-water had an 

 aperient effect. I gathered the salt at the brickfields, and on tlie 

 then newly-built Gatton-park wall, and it appeared concentrated in 

 the water in which they jiuddled tlio clay. There are fuller's earth 

 quarries at Nuttield, in the locality j but I believe the soda in 

 fuller's earth is not in the form of sulphate. I thought at first the 

 sulphur might como from the breeze with which the bricks are 

 burnt J but the deposit in the cellar camo from unburnt clay. 

 There must bo hundreds of tons of it in these clay beds ; and, in 

 certain bricks, it appeared to me to be in sufficient quantity to pay 

 for soaking the bricks. Whether the valley surrounding the high 

 Would uf Sussex was anciently invaded by high tides, and this is 

 iilti red sea salt — how altered ? — or whether it is a frosli-water 

 (lipcisit, may bo questions having some interest; but it would 

 evidently be of immediate advantage to scrub this misplaced aperient 

 from handsome buildings. CURIOSITV. 



TIMBRE OF TRUMPET, ETC. 



[41G]— Can any of your readers tell me how the difference of 

 tone in the trumpet and cornet is to be accounted for ? I have 

 looked into all the books on physics and music I kaow of, but this 

 link between the science and art is wanting. Is the finer tono of 

 the trumpet due to the fact that it has a greater length of tube for 

 the same pitch (as it seems to me to have) ? If so, I suppose that 

 trumpet and cornet have much the same relation to each other as 

 grand and cottage piano have. Or, does the tone of the instrument 

 depend on the number and form of the bends in the tube ? If so, 

 how is the greater difficulty in playing the trumpet to bo accounted 

 for? 



In the horn, trombone, bombardon, i-c, I notice that the tube 

 gradually increases in width from a point near the mouthpiece to 

 the bell (the ratio of increase varying in the different instruments). 

 With this exception, these instruments seem to be exactly similar 

 in form to the trumpet and some forms of cornet, and this makes 

 me think that the number and form of the bends in the tube 

 cannot appreciablj- affect the tono. Information and correction on 

 any of these points will greatly oblige, 1'. E. Swinstead. 



POPULATION OF TllK KAKTH. 



[417]— Adverting to your article, " I'oinil.ntion of the Earth," 

 p. 584, Kxowi.EiiGE, may I be permitted to remark that it suggests 

 a lesson which all moralists and philanthropists may well take to 

 iie.art. 



You show that had mankind during the past -1,000 years been as 

 free from the decimating influences of disease, war, Ac, as. during 

 the past year England lias been, the human race then had been in 

 number sufficient to throng the surface of a globe having a diameter 

 5,000 times that of (ho earth's. Whereas, it is highly probable that 

 the actual number of persons who have existed during this period 

 could stand on a plain in extent less than 70 miles long and CO 

 miles wide. That is, if we may reckon an average population nf 

 750,000,000, and 160 generations of 25 years each. Tl:us— 

 750,000,000 average population. 

 ICO generations. 



120,000,000,000 total population. 



=4,000 square miles. 



30,000,000 to a square mile. 

 But, even taking the present population of 1,. 100,000,000 as the 

 average, and calculating for G,00(l years, then it would appear that 

 the whole human family— all who have had an existence [in that 

 time] — could stand on a plain 150 miles long and 80 miles wide, or 

 little more than the surface of the Principality of Wales. Thus— 

 1,500,000,000 average pojiulation. 

 240 generations. 



360,000,000,000 



12,000 square mile! 



80 miles.— A. WoOD. 



FovD'B F.XTBACT is A Certain care for KbcumMttum and Oout. 

 Pond'* Eitract is a certain cure for H(rmorrhoidi«. 

 Pond'a Extract in a certain cure for Ncural^c pains. 

 Pond-. Eitract will heal Hum« and Woundfi. 

 Pond's Eitract will cure Sprains and liroisea. 

 Bold t.r all C 



I Chemjets. Get the 



