Vol. XXIII. No. lo.] 



POPULAR SCIENCE NEWS. 



149 



Practical Gljonjistry arjd tl?e ]3rts. 



A MEDL^VAL RAILWAY. 



The curious engraving presented herewith 

 is from the Cosmographie of Sebastian Mun- 

 ster, a rare old wori<, published at Basle in 

 1555. It represents in section a mine of those 

 days, and is of very great interest as illustrat- 

 ing the life of former times. 



The most important feature of this engrav- 

 ing, however, is the representation of a tram- 

 wa}-, or structure of rails, for moving the 

 wagons of ore. It has always been supposed 

 that the use of rails, or tramways, origi- 

 nated in the English collieries during 

 the last century, but it is evident that 

 they must date back to an earlier 

 period, probably even much earlier 

 than the date of the engraving, and the 

 real inventor of railroads will never 

 be known. The rails, however, are 

 but a small part of the modern rail- 

 road, and just as much credit as ever 

 is due to Stephenson, Trevethick, and 

 the host of other inventors, whose 

 labors and ingenuity have brought the 

 system to its present development. 



Another remarkable feature is the 

 representation of the individual walk- 

 ing over the ground with a "divining- 

 rod" precisely similar to those in use 

 at the present day. Whether pur- 

 posely or not, the artist has intro- 

 duced an element of caricature into the 

 figure and expression of the diviner, 

 showing, perhaps, that he had as little 

 belief in that ancient piece of hum- 

 bug as the intelligent people of modern 

 times. 



And yet are we sure that the 

 "divining-rod" is entirely a fraud.' 

 As an indicator of the presence of wa- 

 ter, oil, minerals, natural gas, or cur- 

 rents of electricity beneath the surface 

 of the earth, it undoubtedly is, but it 

 does not seem impossible that there may be 

 some personal idiosyncracy dependent upon 

 principles or forces at present unknown to 

 us, which may cause its remarkable move- 

 ments. The superstition has certainly sur- 

 vived for many years, and is probably referred 

 to in the Bible, but, like hypnotism and all 

 other allied psychic phenomena, it is worthy 

 of investigation in a more scientific spirit 

 than has hitherto been accorded to it. 

 Although the "divining-rod" certainly cannot 

 tell us what is below the ground, it may, pos- 

 sibly, at some future time, give us a clearer 

 insight into some of the mysterious forces of 

 Nature. 



We must also make mention of the windlass 

 and ore-baskets, the candles stuck against the 

 walls by a lump of clay, the quaint costumes 

 of the overseer and workmen, and the rude 

 and clumsy tools used by them. In another 



engraving in the same work, a smelting fur- 

 nace is represented, where the blast for the 

 fire is obtained by bellows worked by an 

 undershot water-wheel. One of the work- 

 men is also represented as pushing a wheel- 

 barrow, the invention of which has usually 

 been attributed to Pascal a century later. It 

 is evident that many of our so-called modern 

 inventions are of considerable antiquity, and 

 that the arts were in a more advanced state in 

 medieval times than we are apt to suppose. 

 The engraving was first reproduced by La 

 Nature^ from which we copy it. 



THE USE OF BISULPHIDE OF 

 CARBON IN BOILERS. 



Bisulphide of carbon (CS2) is a light, 

 mobile liquid of unpleasant odor, which 

 possesses many valuable and interesting qual- 

 ities, but the only ones that concern us in 



this article are its low boiling-point (118. 5) 



and the easy condensibility of its vapor back 

 to a liquid. It is not surprising that these 

 qualities should have suggested its use as a 

 substitute for water in boilers, and, to one 

 not acquainted with the principles of the con- 

 seiAration of enery, it would seem as if there 

 was a direct gain in power by using it in 

 place of water, which requires a much higher 

 temperature to change it into an elastic 

 vapor. 



This idea has been the basis of many 

 schemes, both honest and otherwise, of revo- 

 lutionizing our present methods of obtaining 

 power from steam engines. Such schemes 

 are generally periodic, and, as another revival 

 of the bisulphide of carbon engine is about 

 due, it may be of interest to consider the 

 fallacies involved in the theory. 



It is evident, in the first place, that the 



amount of work obtained from a boiler de- 

 pends upon the pressure of the steam or 

 vapor contained in it, and this pressure, or 

 tension, is dependent upon the heat applied 

 to it from the fire in the furnace. Steam at 

 the boiling-point of water has a pressure of 

 15 pounds to the square inch, just balancing 

 that of the air, but, as its temperature in- 

 creases, so does its tension very rapidly. At 

 a temperature of 356" the tension, or pressure, 

 equals 120 pounds to the square inch, or, sub- 

 tracting the weight of the atmosphere, the 

 pressure indicated by the guage would be a 

 little over 100 pounds. 



Now it might be supposed that the tension 

 of bisulphide of carbon vapor was proportion- 

 ately less than that of water, but such is not 

 the case. At 313° the tension is more than 

 four times as great, but here the omnipresent 

 principle of conservation of energy 

 comes in, and we find that to maintain 

 a pressure in our boiler, say of 100 

 pounds, just as much heat must be 

 absorbed by the bisulphide of carbon 

 in the processes of vaporization and 

 heating as by the water. The bisul- 

 phide vaporizes at a lower tempera- 

 ture than water, but in so doing it 

 absorbs proportionately more heat 

 from the fire, and to maintain the 

 same pressure in the boiler while the 

 engine is running, the same amount of 

 heat must be furnished, whether water 

 or any other liquid is used. If this 

 were not the case, perpetual motion 

 would be a possibility, as the steam 

 from a water boiler might be used to 

 run several bisulphide boilers, thus 

 multiplying the energy produced with- 

 out the expenditure of previously 

 stored up energy. 



This principle can be eftectively 

 illustrated by first pouring a few 

 drops of water on the hand and 

 allowing it to evaporate, and then 

 repeating the experiment with bisulphide of 

 carbon, remembering to keep the latter away 

 from fire or light, as its vapor is very inflam- 

 mable. The much greater degree of cold 

 produced — that is, the amount of heat ab- 

 sorbed — by the evaporation of the bisulphide, 

 will be very noticeable. In fact, so great is 

 this absorption of heat by the evaporation of 

 volatile liquids, that it is used to freeze water 

 in the various forms of artificial ice machines. 

 The use of a supplementary bisulphide of 

 carbon boiler, heated by the exhaust steam of 

 an engine, has been suggested, ancf is theo- 

 retically possible. No more power is pro- 

 duced from the coal in such a case, but the 

 heat which would otherwise be wasted in the 

 air would be saved and converted into power. 

 Such an arrangement was formerly in use in 

 a manufacturing establishment in this city, 

 but the practical difliculties in using and con- 



