1841.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



233 



NEW INVENTIONS AND IMPRO\'EMENTS. 



STEAM ENGINE FURNACES. 



ESPERIRSENTS ON THE ECONOMICAL EFFECTS OF FURNACES OF DIFFERENT 

 CONSTRUCTION, AND ON DIFFERENT KINDS OF FUEL. 



These experiments have been made by a committee appointed by the 

 Society of Industn' of the Grand Duchy of Hesse, and their object lias been, 



1st.' To ascertain tlie useful and economical results of furnaces for boilers 

 constructed on differeut principles. 



2nd. To establish the relative value of the combustibles most gencrally 

 used in the country. 



We do not consider it necessary to enter into the details of the experi- 

 ment ; we will only mention the results. 



In order to decide the first question, a common boiler was set over a fur- 

 nace of brickwork provided with a chimney, and this apparatus for heating 

 was submitted to various modifications, as regarded the form and structure 

 of the hearth as well as the disposition of the flues. 



In order to resolve the second question, experimental trial was made of 

 good dry wood chopped from the beech tree ; of good coal from Roer, called 

 Fettschrot ; and of square pieces of turf from Greishcimer, perfectly dried, 

 and of the heaviest kind. 



The different modifications used in the construction of the furnace were 

 the following : 



I. Furnaces without flues or draught chimneys, the boiler being suspended 

 freely above the fire. 



II. \ simple flue passing round the boiler, the bottom part of which only 

 was immediately exposed to contact with the fire burning in the grate. 



III. A double flue, that is, a flue going twice round the boiler in the same 

 direction. 



IV. A stove arched in the shape of a cupola, and having an opening in 

 the middle of the arch, which became gradually wider towards the top, and 

 by which the heat ascended, and was communicated to the bottom of the 

 boiler, to be afterwards conveyed by three holes, placed at regular distances, 

 into a circidar passage which surrounded the boiler; to issue thence through 

 three similar apertures difterently arranged, and which communicated with 

 a second passage placed higher, whence the draught was at length conducted 

 into the chimney. 



V. Two half flues, that is, each of which did not extend beyond half the 

 circumference of the division of the boiler. The fore part of the flame (on 

 the side next the door) ascended from the stove, and was distributed half 

 into the flue on the right, half into the flue on the left, and was finally con- 

 ducted into the chimney at the point where they met. 



VI. Four half flues, or two on each side the boiler (from right to left) ; 

 the flame issuing from the side opposite the door entered into the lower flue, 

 then passed half the circumference of the partition of the boiler, and entered 

 into the upper flue, whence it was finally conducted into the chimney. 



The relative effects of these difterent arrangements have been ascertained, 

 both with respect to the quantitj- of water evaporated in the boiler, as well 

 as that of the combustible employed ; particular care being taken to keep up 

 the same level in the boiler after each experiment. 



In the following table, which contains results of the experiments, the nu- 

 merals indicate the different methods of construction of the furnaces in the 

 order in which they have been described above ; the figures placed imder- 

 neath indicate the relative qualities of the combustibles employed to obtain 

 a similar result ; consequently the greater amounts indicate the worst methods 

 of employing combustibles : — 



„ , 1 VI V III II IV I 



°°" J 63 68-8 68-69 72-19 72-23 100 



,p^ -I VI III IV V II I 



^™^ J 53 66 71 72 76 100 



P„ , \ III IV II V IV I 



^°^ J 73 76 83 85 91 100 



The following are the conclusions to be deduced from the foregoing table • 



1. The fire over which the boiler was placed without flues was attended 

 with a less advantageous use of combustible than those with flues. 



2. The utility of flues is much more perceptible in fires of wood or turf 

 than in coal fires, because the result is a saving in fuel of about one-fourth to 

 one-third mth wood, and almost of one-fourth to one-half with turf, and 

 only of one-tenth to one-fourth with coal, by the addition of flues. 



3. The mode of construction with four half flues (No. VI.) may be con- 

 sidered to be generally the most advantageous. Next to this the construc- 

 tion with a double flue (No. Ill), which in its mode of action bears the near- 

 est resemblance to it. With respect to the arrangements Nos. II., IV., V., 

 the effects they produce are nearly similar. 



4. The double flue (No. Ill), which surrounds the whole boiler, is at- 

 tended with better results than the single flue (No. II) ; according to the 

 same principle, four half flues (No. VI) are attended with better results than 

 two half flues (Xo. V). 



5. With the fire of wood and of turf, two half flues (No. V) have more 

 efifect than a whole flue (No. II), and four half flues (No. VI) more than two 



whole flues (No. Ill) ; in short, flues which encircle only half the boiler are 

 in this case more effectual ; while with a coal fire it is precisely the contrar)'. 

 The cause of the difference is doubtless this, that in such combustibles as 

 wood or turf, which blaze brightly, a retardation of the heated air, which 

 in these half flues produces a sudden change in the direction of its motion, 

 is more advantageous than with coal. 



With respect to the calorific power of the diflferent fuels, there results from 

 equal weiglits of turf, 96, and of coal, 250, when that of wood is considered 

 equal to 100. 



The great difl'erence that is found in combustibles, with respect to their 

 natural quality and their composition, as well as in their degrees of dryness, 

 can scarcely admit of forming points of comparison between these latter re- 

 sults and any other given case. It is well known that there are turfs which 

 from an equal weight throw out more heat than wood ; but the results with 

 respect to the different methods of constructing furnaces are more to be de- 

 pended on ; because in these are remarked a degree of regularity in their 

 effects, and it is easy to account for the causes on which the differences de- 

 pend. — Moiiifeur Indiistriel. — Itwenfor's Advocate. 



LOCOMOTIVE EXCAVATOR. 



This French machine is stated to be the invention of M. Gervais, of Caen. 

 The trial of the apparatus was made in the presence of a committee of the 

 Society of Emulation at Rouen, and of many of the distinguished residents of 

 the tov.'D, and the result is said lo have left no doubt of the possibility of 

 making excavations by tlie j)ower of steam. It is said to be particularly 

 applicable in digging canals, and makir.g the excavations for railways. The 

 apparatus is placed on a large heavy kind of carriage, in the fore ])art of 

 which there is a steam-engine of six horse power, witli oscillating cylinders 

 and a tubplar boiler, which works the machine, and also turns the two fore 

 wheels very slowly, so that the whole is gradually moved forward as the 

 work progresses, lai'ge pieces of wood being laid down to form temporary 

 rails over which the machine is propelled. Towards the back of the machine 

 there are two machines similar to dragging machines, which raise the earth 

 that has been dug out, and deposit it in a horizontal endless chain of I-uckets. 

 which carry the excavated earth beyond the limits of the trench, and there 

 deposit it, forming an even and regular bank on each side. The excavating 

 apparatus is placed about the middle of the carriage. It consists of four 

 iron shafts parallel to each other and equi-distant, the whole four liaving 

 their axes in the same plane, and forming an angle of fifty degrees to the 

 horizon, the incline being towards the back of the machine. Each shaft has 

 attached to it five double arms, equi-distant from the bottom to the top, and 

 each arm is furnished with a spade-shaped tool. These shafts, therefore, 

 present forty spades working at difterent heights, which dig a ditch nearly 

 three metres in width and upwards of one metre in depth. Each of these 

 excavating tools when in action strikes against the earth ten times in a mi- 

 nute. These revolving excavating shafts are put in motion by the steam- 

 engine, and the action of the engine is so regulated that the whole nirchine 

 progresses at the rate of about twelve metres an hour. The whole of the 

 machinery, including the carriage, weighs about 24,000 kilogrammes, or 15 

 tons. When, owing to the nature of the soil or the presence of large stones, 

 the action of the tools is resisted, the locomotion is stopped, and the whole 

 apparatus is made to back, so as to enable men to remove the obstruction. 

 The trenches dug by this machine are vei-y exact, the sides are perpendicular 

 and smooth, and the earth thrown out forms on each side a regular em'iank- 

 menl. A machine of this kind was some time since shown by M. Gervais to 

 the French Academy of Sciences, on wliich they reported very favourably, 

 but it was not provided with the means of locomotion, nor was it on so large 

 a scale as the machine at Rouen. Ibid. 



C.^LOTYPE. 



It has been known for some time, that Mr. Fox Talbot, in the progress of 

 his experiments to render more perfect the art of photogenic drawing, had 

 discovered a means by which paper could be made far more sensitive to light 

 than heretofore. The impressions, however, so quickly obtained by this new 

 method, are in the first instance invisible, but by a process similar to the 

 first, they are made to appear with even greater power than in ordinary 

 photogenic drawing. On Thursday evening, June 10, Mr. Talbot read a 

 paper at the Royal Society, in wliich he described the new process, called, 

 for distinction's sake, Calbtype ; and as the subject is one of general interest, 

 we shall here briefly describe it : — The paper is covered with iodide of silver, 

 by washing it successively with nitrate of silver and iodide of potassium. 

 Aiterwards it is washed over with gallo-nitrate of silver, the greater part of 

 which is removed by immersion in water, but enough adheres to render the 

 paper exceedingly sensitive to light. The paper is then dried, and placed in 

 the camera obscura, and the image of a building, or other object, is generally 

 obtained in less than a minute. This image, however, is usually quite in- 

 visible ; and the mode of rendering it visible (which is the most curious part 

 of the Calolype process,) consists in washing it again with gallo-nitrate of 

 silver and then gently warming it, which generally causes the appearance of 

 the picture with great force and vivacity in the space of a minute or less. 

 The gallo-nitrate of silver is formed simply by mixing solutions of nitrate of 



