170 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Junk, 



Reference to fig. 1 cxIiibKs the general arrangement of the apparatus in 

 question. It consists of a set of two or more tall opriglit air-light chambers 

 or vessels which are supplied with steam from a suitable low pressure boiler : 

 these vessels may be ol any suitable capacity, the dimensions figured in will 

 show what is intended in this respect. In order to produce tlie vacuum by 

 such apparatus, steam is in the first place permitted to flow in at the vpper 

 end of each vessel, which steam as it enters is forced to occupy the upper 

 part of these vessels and as it continues to flow in (without in the slightest 

 degree minghng with the air), it depresses and forces out at the valves below 

 all ihe contained air. It is important to remark that by the peculiar mode in 

 which the steam is admitted to these chambers there is not the slightest 

 mingling of the air with the steam— the stratum separating the two is as per- 

 fectly defined as if the steam were a piston descending and expelling the air 

 out at the bottom as it gradually occupies the place of the air. This system 

 of vertical displacement is the grand feature of the invention. As soon as the 

 air is all gone from A B and C, the valve V is moved into the position as seen 

 in fig. 2. and the injection of cold water admitted to the condenser C, the re- 

 sult of this is the instant formation of a very perfect vacuum in vessel B ; 

 this tieing the case the valve H is opened to the atmospheric railway main 

 pipe M, and such portion of the air withdrawn from it as is due to the relative 

 capacity of the pipe as compared with that of the vessel B. 



The moment this is accomplished the valve V ia slid along into the position 

 fig 3. the consequence of which is an immediate transfer of nearly all such 

 portion of steam from vessel A as the contents of B was, minus the balance 

 of the atmosphere ; in this action B acts on the contents of A as a sort of 

 preliminary condenser, w ilh this important advantage, that we employ a con- 

 siderable portion of the steam that was in A to refill the vessel B, and so pre- 

 pare it for the admission of fresh steam from the boiler. The valve V con- 

 tinues to slide on into position fig. 1, when the entire steam remaining in A 

 is condensed by C, and ils contents left in the state of nearly perfect vacuum ; 

 the valve F is then opened to the atmospheric pipe M, and A then abstracts 

 it contents, or nearly so, from M, so that at each alternate action of A and 

 B we have the same action as if A and B were (as they really in effect are) 

 vast air pumps, the steam acting in them as a piston, but with this important 

 advantage that there is no friction whatever. Some idea of the rapidity with 

 which steam can in such a case flow into and be withdrawn from such vast 

 chambers cr vessels, may he formed by referring to the rapidity of action in 

 the case of large steam engines, the action of steam flowing in and out of 

 such vessels under such circumstances as required or presented here is nearly 

 as quick as thought. 



So that all that is requisite to cause these two vast vessels (or as many 

 more as may be thought requisite to act as a set) to act as air pumps is simply 

 to cause the valve V to push backwards and forwards, as indicated by the 

 positions in figs. 2, 3, and i, in all ordinary cases 4 or 5 fills of such vessels 

 as indieated in fig. I, would extract the air from the atmospheric pipe be- 

 tween station and station and bring all into action. 



One very important advantage in this most simple and direct mode of pro- 

 ducing vacuum directly is this, that previous to the starting of the train 

 the entire set of four great chambers may be previously l)rought into the 

 condition of one vast magazine of vacuum, so that on the signal being given 

 all that has to be done is to open the valve leading to the atmospheric main 

 and in an instant such will be the energetic effect of this chamber of vacuum 

 on the long valve as to cause it to close down tightly all at once, and so en- 

 tirely remove the risk of that leakage w hich is certain to exist for a long time 

 in the case of gradual exhaustion by the comparatively slow action of the air 

 pump; this gradual closing of the valve is one of the most fertile sources of 

 loss of p.nver in the present system, but by the energetic elfect of a rapid air 

 exhaustion, as here proposed, not only would the valve be closed tight down 

 all along the length, but also such a vacuum formed in the pipe as to be in 

 all ordinary cases quite equal to do the duty of drawing the train along. In 

 order to render the action of the valve V self acting, there are two small 

 tanks of water at L and N placed directly over the discharge valves E, G, 

 the action of these are as follow — suppose the air being expelled from chamber 

 A, this air would pass out by the valve E, and bubbling up through the water 

 in the tank L some of it would collect under the gasometer IC and raise is up, 

 there being a hole in the top of this gasometer or inverted tank K it viill be 

 kept in suspension just so long as there is air being given oat from the valve 

 E, the instant the last bubble of air is gone out, and the steam begins to 

 meet the water, K is no longer sustained, and sinking down by reason of the 

 escape of the air from the hole at the top as it sinks it draws the valve V 

 across into the desired position, and then the tank N begins to prepare in like 

 manner for the performance of its duty. Thus is given to the machine a 

 power of nice discrimination as to the e.xact moment when all the air is gone 

 out, and consequently the proper time to reverse the action of the valve. 



The entire success of the enterprise, Jiowever, depends on the vertical dis- 

 placement ; any attempt to dislodge air by steam directly by any other means 

 would not answer. Experiments on the subject show that such is the differ- 

 ence in the specific gravity of steam of low pressure, especially as compared 

 with atmospheric aii'; that if steam be permitted to enter gentli/ at (he upper 



end of a tall upright vessel, in that case the plane of separation of the 

 sleam from the air will be found to preserve a verj- remarkable integrity of 

 strata — air is the woist material to convey heat by communication dow.nwakd- 

 Consequently as the steam flows in at the lop it soon forms (at the stratum 

 of separation) a quiescent bed for itself to rest on, which goes down aloi g 

 with the descending column of sleam to all practical intent like a piston with 

 no friction. 



It is proposed to line the inside as well as the outside of the chamber with 

 wood to keep it warm, and so prevent the air from robbing us of heat or 

 fuel. ]n order to secure a gentle flowing in of the steam in an uniform de- 

 scending column the low pressure steam is at first let in very gently, and as 

 an additional precaution against any mixture with Ihe air a cup ordish-formed 

 plate is placed opposite the entrance-pipe, which assists the lateral or hori- 

 zontal diffusion of the steam ; as a second precaution a perforated plate is 

 used, which further has the effect of preventing any undue local ilistutbance 

 of the column of air ; the result is th it the steam descenils with a horizontal 

 understralum like ihe clouds on a fine summer day, resting on the top of the 

 column of air and depressing it, and forcing it out at the front exit valve 

 below, which affords a very free exit for it. It is not intended in practice to 

 apply the leaky gasometer to do the valve moving duty direct, but simply as 

 in the case of a pumping engine to draw the bolt which permits the valve- 

 moving agency to come into action, asniall portion of our magazine of va- 

 cuum will supply ample means of obtaining the valve-moving agency ; but if 

 the apparatus were done on a scale large enough one supply of steam to the set 

 and one condensation would form cubic ci.ntenis of nearly pure vacuum quite 

 equal to the exhausdon of the pipe to the moderate amount they require, 

 viz, 81b. or so; the energetic effect produced on the long valve by the 

 opening the main to such a chamber or magazine of nearly pure vacuum 

 would cause the long valve to flap down tight in an instant, and so save a 

 vast amount of loss of power and lime as at present, when it has to remain 

 in a leaky condition till the air-pumps have brought the vacuum to the valve- 

 closing point." 



DIFFERENTIAL STE.tM ENGINES. 



John Grieve, of I'ortobello, Edinburgh, engineer, for " ce> tain Improvements 

 in the production and use vf steam applicable to steam engines."— -Granted Oct. 

 17, ISM; Enrolled April 17, 1845. (IVith Engravings, see Plate Xf I.) 



The first improvement is founded on the principle that small additions of 

 temperature produce a great increase in the expansive force or power of sleam 

 which increases with the temperature, and that high temperatures are easier 

 maintained as the cooling medium is diminished ; to eftert this the inventor 

 uses two or mure steam vessels, ft generator and receiver or receivers, bolli or 

 all closed to or from the atmosiihere, and having regulating valves of different 

 loads, the lesser load on the receiver. 



The steam after being formed in the generator is passed into the receiver, as 

 hereafter described, where its expansive force is diminished, and the wafer in 

 the receiver being only what is required for the production of steam, is raised 

 to any degree of heat that may be wanted, less than the temperature in liia 

 generator, by means of loading the valve of the receiver to a greater or less 

 extent ; the water in the receiver, after being heated, is forced intu the gene- 

 rator by a pump. Steam engines formed on ihis principle the inventor names 

 '■ Differential Steam Engines," as it is from the difference of temperature be- 

 tween the generator and receiver that the power for propelling the engine is 

 derived. 



The inventor makes seven different claims for generating sleam in a sepa- 

 rate vessel called a generator, and collecting the steam therefrom in another 

 vessel called a receiver, either before or after it has driven the engine fur the 

 purpose of heating the water in such receiver, to be raised into steam for 

 driving an engine, or for feeding the generator with hot water. One of tlie 

 arrangements is shown In the engravings, figs. 1 and 2, Plate XVI. 



In the drawings the same letters on each figure of tlie same vessel refer to 

 the same parts. Fig. 1 is a vertical section of a spherical shaped steam 

 boiler or generator; A the furnace, B ash-pit, C flues leading from each side 

 of the furnace to D, which is a horizontal flue stretching across the lower 

 part of the boiler, E a vertical flue on the top of which is placed a funnel. 

 (In land engines the boiler may be surrounded by a dome of brick or mason 

 work, leaving a space between for the flame and smoke to circulate witli a 

 flue taken from tlie bottom of the casing, or any other part as may he de- 

 sirable to the chimney.) F a tube made of boiler plate, on the top of which 

 is placed the plate G, for the safety valves H. 1 lever, K rod for regulating 

 the pressure on safety valves, L furnace door, M damp r plate, N sleam pipe, 

 sludge pipe, V door (lined inside with fire brick) for cleaning out flues, see 

 fig. 2 i Q man-hole door, R pipe for supplying tlie generator with water from 

 receiver delivered at Z, S force pump to supply the generator with water, T 

 two-way cock, V boxes for valves opening towards ihe generator, W pipe for 

 returnii.g surplus water to receiver, X casing for flue E, a open cr perforated 

 plate near the surface of the water to keep the water from shifting heavily. 

 Fig, 2 is a vertical section of the receiver (a cylindrical sliapeil vessel with 



