April, 1904.] 



KNOWLEDGE c^- SCIENTIFIC NEWS. 



73 



devoted to experimental work di'siL;iu ,, , note the joint 

 interests of the nation's manufacturing industries (in the con- 

 duct of which appUed knowledse is requisite) and theoretical 

 inquiry of a scientific character. Probably few of the .general 

 public who visit Bushey Park in such numbers are aware of 

 the proximity of the National Physical Laboratory, still less 

 of its. aims, .although it is a public institution maintained by means 

 of the taxpayers" money. Here, however, a great work is unob- 

 trusively going forward.whose benefits spread themselves far .and 

 wide. Many .and varied are the investigations pursued. In 

 electricity, for example, is one on the effect of temperature on 

 the insulating properties of materials used "in dynamos, 

 motors, and transformers; in thermometry a researcli on the 

 specific heat of iron at high temperatures ; in metrology, the 

 standardization of the steel yard and nickel metre; and in 

 metallurgy a series of tests on nickel steel. Then, in the de- 

 partment of engineering, experts say that the inquiries in 

 hand are eminently useful to a producing country such as 

 England is, and hopes to remain, despite her foreign competi- 

 tion. Comprised in electrotechnics are tests on electrical 

 instruments, ammeters, wattmeters, voltmeters, and other in- 

 dispensable adjuncts to the needs of industry, .\gain. in 

 chemistry, optics, and photometry, the record of investigation 

 bears the same tendency. 



The laboratory is, of course, a young organisation as yet ; 

 but its operations are ramifying in all directions under the 

 able giuidance of Mr. K. T. Glazebrook. F.R.S. But, as Lord 

 Rayleigh, the Chairman of the General Board, pointed out the 

 other day, unless adequate funds are provided to meet the 

 national purposes of the foundation the institution must fail 

 in accomplishment, and a starved laboratory would jirobably 

 prove a worse evil than none at all. Besides, it should be 

 borne in mind that Paris and Washington have recently fol- 

 lowed the example of London in initiating standardising 

 establishments intended to help national industries each, too, 

 is subsidised in a far more liberal way than in our own case. 

 The necessity for making better provision for the needs of the 

 laboratory has lately engaged the earnest attention of the 

 Executive Committee, and representations have been made 

 to His Majesty's Treasury- on the subject. A detailed scheme 

 for the future organization and development of the institution 

 has been drawn up and submitted. This, if approved, will 

 entail a revision of the existing Parliamentary grant-in-aid. 

 but in view of the special functions of the laboratorv, and the 

 sphere of usefulness that lies before it, strong hopes are enter- 

 tained of a favourable issue to the appeal. 



COR.R.ESPONDENCE. 



A Novel Electric Traction System. 



To THE Editors ov •' Knowledge." 

 Sirs, — The scheme described under the above heading in 

 your March issue, taken from the Ekctrotechiiisclwr Aii^.cii^cr, 

 presents such curious features that one is inclined to doubt 

 whether it has been put forward seriously. To use electricill v- 

 heated steam-engines in preference to electric motors would 

 appear, at any rate at first sight, as an absurdity, as the 

 following considerations will show. 



It may be safely assumed that the internal thermal efficiencv 

 of a steam locomotive does not exceed 10 per cent., I'.t'., only 

 10 per cent, of the thermal energy carried by the steam froin 

 the boilers into the cylinders is converted into work on the 

 piston. So that, accepting 90 per cent, as the efficiency of the 

 electric heaters, and assuming the mechanical efficiency of the 

 engines to be as high as go per cent., it follows that of the elec- 

 trical energy supplied to the V)oiler all that is available for 

 propulsive power is go per cent, of 10 per cent, of 90 per cent., 

 i.e., about S per cent. Against this the ordinary electric loco- 

 motive would have, as stated in the article, an over-all 

 efficiency of 60 to 70 per cetit., or even more. 



Now although the actual energy for a water-power installa- 

 tion in a sense costs nothing, the plant to develop it is very 

 costly ; and it may be safely predicted that it would not pay 

 to use a generating plant and transmission system eight or 

 nine times too large to save scrapping the steam locomotives. 



This very large ratio .against the electro-thermal system 

 would, it is true, be reduced by the fact that every locomotive 

 would to some extent act as an eiiualiscr of the demand on the 

 power-houses, reducing the excess plant that would ha\e to be 

 installed ; but the larger system worked from one powerhouse, 

 the less this advant.agc would becoTuc ; .ind in ;iny c.isc the 

 excess of power retjuired by the electro-thermal system would 

 be enormous. 



Even if under any conceivable conditions such a system 

 might prove advantageous, it is certain that the figures put 

 forward to justify the proposal are mitirely erroneous; and 

 this confirms one's doubts as to the scheme having emanated 

 from any authoritative ([uarter. 



The first point to be noted is that it is proposed to raise 

 the temperature of the water from 10" to up C. recpiiring 

 iHo calories per kg.; but lyo" C. is said to correspond to a 

 steam pressure of 50 kg. per sq. cm. As a matter of f.ict, 

 iqo° C. (= 374" F.) corresponds to satur.ited steam at about 

 170 lbs. per square inch (above atmosphere), whilst 50 kg. per 

 sq. cm. is equivalent to 710 lbs. per square inch. However, as 

 pressure is not referred to further by the writer this discre- 

 pancy does not matter much. 



But next it is said that to raise 4000 litres of water through 

 180" C. will take 4000 X 180 = 720,000 calories; this is true 

 if it remained water, but this amount of heat is by no means 

 enough to convert the water into steam, i.e., to provide the 

 so-called latent heat of evaporation. So that, whilst it might 

 be correct to say that a consumption of 1000 kg. of hot water 

 per hour at lyo" C. would take zz^ kilow.itts, it is very far 

 from the truth to say the same of 1000 kg. of steam. 



To convert 1000 kg. of water at 10- C. into steam ;it i()o' C. 

 will take, not 180, but about 635 calories per kg.; in other 

 words. 635,000 calories per hour must be provided ; and if 

 I calorie in the boiler requires i'275 watt-hours, the electrical 

 energy will have to be supplied at the rate of 810 kilowatts, or 

 more than three-and-a-h.alf times the figure given. 



.\n electric locomotive taking 810 kilowatts might be relied 

 upon to give 700 to qoo effective horse-power; the electric 

 steam locomotive taking the same electrical power, and evapo- 

 rating steam at the rate of 1000 kg, per hour, would not give 

 more than 100 to 125 effective horse-power, if so much. 

 Your obedient servant, 



.A K SOLD G, Hansard. 



53. Victoria Sti'eet. Westminster, S.W'., 

 March cj, 1904. 



Snake Stones. 



To THE Editors or " Knowledge." 



Sirs. — Some time ago I was much interested in a series of 

 articles in the scientific column of a weekly paper on the 

 subject of " Snake Stones." Nothing was said at the time in 

 connection with Brazil, and as I lived in th.it country for 

 several years it may be interesting to some of your readers to 

 have a word on the subject. " Snake stones " are not stones 

 at all. at any rate not in Brazil, and I should think they would 

 be much the same all over the world. • In the articles above 

 referred to there appeared to be gr*-at doubt as to what they 

 are. The only ones used in the part of Brazil where I was 

 were made from the horns of young deer, burnt or carbonised 

 in a peculiar manner, which leaves it very suctorial, and which 

 is kept as a close .secret by a very few men who make them 

 for sale or barter, and try to make out that they have alu)ost 

 supernatural power to heal snake bites. They are usually 

 sold in pairs, and are not by any means common. In form 

 they are about one inch in length, four-sidcKi, and slightly 

 tapering to one end. When anyone is l>itten by a snake, one 

 of these " stones " is placed on the spot and held close, while 

 a band of some sort is tied tightly round the limb a little way 

 back towards the trunk. The " stone " is allowed Jo remain . 

 on the wound until its own weight makes it f.dl ofl, when it is' 

 presumed all the poison has been extracted. It is then 

 dropped into milk and allowed to soak. It is said th.it if 

 the person is to get healed theiailk will turn to ,i dark bniwn. 

 colour, the fact being, I suppyse.'fMat the blood held by tge . 

 stone has that effect. As usual 'with these things, there are 

 many superstitious beliefs in connection with these "stones," 



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