1816.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



215 



at tbe rate of 11 feet a minnle, which it must be for good ventilation, the 

 quantity of air discharger) must be 2,303,000 cubic feet per minute. Now 

 the whole of this 2,000,000 cubic feet of air must be heated sulliciently high 

 to produce an available power, by the difference in the weight or balance 

 of the internal and external columns. A temperature of 300 degrees Fah. 

 believe, is necessary to produce any available pressure. The whole of 

 the air must, therefore, be passed up the chimney, and then raised to a 

 temperature of . 500 degrees of heat as it passes. This appears to be im- 

 practicable. But supposing it possible, the quantity of fuel burnt could 

 never be suffered. On referring to experiments made by myself some years 

 since, I find a pound of charcoal will heat 1,000 cubic feet of air from 60 

 degrees only to a temperature of .500 degrees. Therefore, if we take this 

 as sufficiently accurate and favourable data, we shall find that we require 

 at least 2.000 lb. of fuel per minute. The impossibility of being able to 

 consume this quantity of fuel is evident; it is not possible to burn this 

 quantity of fuel. To produce practically a discharge of that quantity of 

 hot air, or effect an available power, it must be borne in mind that air raised 

 from CO degrees to 500 degrees doubles its volume. 



You object, also, to the system of ventilating from the floors or sides of 

 the room instead of from the upper portion of the apartments? 



Yes ; there is a practical objection to this direction, which will be seen 

 by looking at the subject carefully. These retrograde currents produced 

 from air entering at a low level into a room are practically very objection- 

 able ; they produce an increased rate of evaporation upon the skin, which 

 produces a sensation of cold. Although the temperature of the air in mo- 

 tion itself may be warm — say 70 or 80 degrees — it will produce a tempera- 

 ture very considerably lower on evajiorating surfaces. The skin of the 

 human body is essentially an evaporating surface, and suffers much from 

 this law. The feeling of cold in the parts of a room where retrograde or 

 direct currents act is not due to the actual temperature of the currents, but 

 to the increased rate of evaporation produced by them. Evaporation pro- 

 duced by retrograde currents rapidly absorbs heat. A person cannot get 

 out of the influence of the direct or retrograde currents if they enter near 

 the floor or at a low level, but if the openings are made in the ceiling or at 

 a high level, then they are mixed with the atmosphere of the room above, 

 and cease or become destroyed before they can possibly reach any one 

 standing on the floor.j 



Although not evinced by the common thermometer? 

 Not by the common thermometer, but instantly by aa evaporating ther- 

 mometer. 



It does not depend upon temperature, but evaporation ? 

 It is entirely due to the increased rate of evaporation produced by a cur- 

 rent of air passing over tiie surface. It is said, "If you cover the skin 

 with ether, or some other rapidly evaporating substance, you may freeze a 

 roan to death in the height of summer." A current moving at the rate of 

 three miles an hour, acting on highly alcoholic ether placed on (he surface 

 of a thermometer, will occasion the mercury soon to fall to the freezing 

 point, notwithstanding the current of air may he at 80°. Evaporation 

 where there are partial currents goes on unequally ; there is a feeling of 

 heat out of the currents, and a feeling of disagreeable cold when in them. 

 You cannot get out of them if the entering current is anywhere where it 

 impinges upon the person. There is a great objection to air for ventilation 

 entering a room anywhere at a low level; it must necessarily irapigne upon 

 the person. 



Will you state what force you propose to apply to set the atmosphere in 

 motion ? — I prefer the ris <i tcrgo arising from the escapage of high-pres- 

 sure steam ; through proper sized air passages it furuishes a power capa- 

 ble of being managed so as to produce at will any rale of current down to 

 almost an insensible breathing. I prefer if, also, in consequence of its 

 great capability of management. M hen I state that in some experiments 

 which I made ten years since, I raised a column of mercury nine inches 

 by the force of the current of air produced by it, the C'omraillee may see 

 from that fact that it is capable of producing a force which never can be 

 required for ventilation. M. Arago, in some experiments within the last 

 few months, has raised by a current of air thus produced a column of mer- 

 cury 15 inches. Therefore these facts prove that we have abundant power 

 so as to overcome every opposition arising from wire drawing or other re- 

 sistance, and to compel air to pass with uniformity wherever it may be 

 necessary. It is simple in application, and its economy great, though that 

 is not of so much consequence as the former ; it is capable of being passed 

 easily and independently to any part of the building separately. You may 

 act by this principle upon groups of rooms, or upon single rooms, or any- 

 where where it may be convenient ; by that means, you prevent the neces- 

 sity of cutting up the building, or the making of large communications. 

 Another advantage which it will produce, and which though last may not 

 he the least, is, that it is capable of passing a sufficient quantity of air, as 

 much as can be required to produce ventilation, through small passages, 

 which passages may be secured against the communication of flame, iu 

 case of tire, on tlie principle of the safety lamp. This is a circumstance 

 of great importance where a building is to be made fire-proof. Supposing 

 there are several rooms connected together by ventilnting flues, all would 

 be rendered safe and perfectly independent of each other as to fire by the 

 intervention of diaphrims of wire gauze, upon the principle of Sir Hum- 

 phrey Davy's safely lamp. Wire gauze cannot be introduced unless you 

 have great command of power, because you offer by it a strangulation dif- 

 ficulty in the passage of air, which cannot be overcome by the ordinary 

 msans of ventilation. 



You consider ibis principle perfectly applicable to fire-proof buildings— 



that it does not affect the fire-proof quality of the buildings in any way? 



Not at all ; but if there should be any doubt as to the safety of a wire 

 gauze disc, or layers in succession, each room may be ventilated independ- 

 ently of any communication made between them ; in that case it must be 

 self-evident that there can be no danger from fire. 



So that the system may be applicable either to single rooms or to an en- 

 tire building ?— Yes ; the power is suflicient to produce ventilation for the 

 entire building. 



You are aware that Dr. Reid's view of taking the air, by which the 

 houses are to be supplied, f.om the top of this great tower, when com- 

 pleted, is for the purpose of getting a purer atmosphere than he thinks he 

 can get down near the river, where it is, in a degree, vitiated by sewers 

 and smoke ; do you think that it would be advantageous to get your air 

 from such a source for the general ventilation of the buildings? The sew- 

 ers I know little about ; but in regard to smoke, the most deleterious and 

 injurious products of combustion in London from the chimneys I believe 



are those which are invisible. The visible smoke— the unburnt carbon 



we need not be much afraid of; it blackens our laces, but I believe does 

 no harm to our lungs. The most serious injury is from the sulphurous 

 acid formations, and from some of the volatilized metallic oxides : but this 

 is a question of great difliculty, a question that much better chymists than 

 I am must answer. 



Do you mean to imply that you doubt whether air two or three hundred 

 feet high is not likely to be loaded with much greater impurities than the 

 lower atmosphere, which appears to be coarser ! — Yes ; I should have 

 some doubt about it. 



You are aware that Dr. Reid has a plan for collecting the smoke of 

 every fire in the building, and conveying it all through one shaft? — I have 

 heard so. 



Do you believe that cao be done?— I think it is very difficult. 



SUBSTITUTE FOR RAILWAY SLEEPERS. 



The following suggestion occurs in the Engineer's eleventh report to the 

 Georgia Central Railroad Company, (America): — 



During the past year, I have made an experiment of substituting iron 

 cross ties for our present wooden sleepers. In renewing the sleepers as 

 they decay we use no other timber than cypress — this is uot to be obtained 

 near the road above the Ogechee river, and we are obliged to transport 

 the sleepers from the lower portions of the road, which increases the 

 labour and expense. 



1 have long entertained the opinion that a much smoother track could 

 be attained by removing entirely the sleepers, which support ihe string 

 pieces at intervals, so as to give the string piece a continuous and uninter- 

 rupted bed of earth. I am now convinced of the correctness of this opin- 

 ion. The plan is as follows : — 



The string pieces (6 by 12 inches) are laid on an even, well rammed 

 surface, and iu length of from 30 to CO feet — at the joinings, a bolster 

 piece of the same scantling as the string piece and three feet long, is placed 

 lengthwise immediately under the joint, and the string piece pmned to it. 

 The iron rails, of the ordinary j, pattern, are laid along the centre of the 

 string piece, and the track is kept in gauge by the iron tie, a piece of fiat 

 bar iron, half an inch thick by two inches wide ; this tie is let flatwise 

 into the string piece, flush with its upper surface under the rail, and the 

 ends, bent into the form of a hook, grasp the outside of the bottom web of 

 the rail at the joint. The rail is confined in other respects as usual with 

 the ordinary hook spikes. The track is filled even with the top surface of 

 the string pieces. We have laid about seven hundred feet in Ihe manner 

 above described, on a portion of the road where the earth was sprinjy 

 and it was difficult to keep the track in adjustment. It has borne tiie 

 transit of the trains for several months past, and keeps in much better 

 order than with Ihe wooden sleepers. The follovv*ig statement shows Ihe 

 comparative expense of a mile of road with iron cross ties, as above de- 

 scribed, and with wooden sleepers, for twenty years : — 



With Iron Cross Ties for one mile. 

 352 iron bars, 181b. each, at 4 cents per lb., . . . 233-44 dollars 

 Bending Ihe ends and preparing them, at 4 cents each . 14-08 „ 

 330 bolster pieces under the joinings of string pieces (G by 

 12 inches, and 3 feet long), at 7 dollars per thousand 

 feet, B.M., to ba renewed three times in 20 years . . 166-32 „ 

 Putting in 352 ties 57-12 



Amount .... 

 With Wooden Sleepers for one mile. 

 660 cypress sleepers, allowing them to be left sound at the 

 end of 20 years, will have to be renewed three times ; 



then 1980 ties at 25 cents each 



Putting in 1980 ties 



490-26 dollars 



49500 dollars 

 471-24 „ 



Amount .... 966-24 dollars 

 Difference in favour of iron cross ties ia a period of 

 twenty years, per mile 475-28 



