182 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



Jl'NB, 



timi of those of water, ran produce a volatile acid and a fixed 

 base, the evolution of this acid and the liberation of tliis liase 

 will be determined by passing a e urrent of aqueous vajxiur over 

 the salt raised to a' lii:;li temperature. W'lien either tlje acid or 

 base to be liberated forms a ciimliination with water wlii<^li can re- 

 sist decomposition l)y the heat emjiloyed, the tendency to form such 

 hydrates adds mucji to tlie decomposing power of the aqueous 

 vapour. Altliougli potasli and soda are not by themselves fixed 

 l)ases at liiirh temperatures, yet by tlie use of the substances 

 before mentioned, tliey can form combinations which are fixed, 

 aiid by this means their salts come under the above rule. 



The actual number of salts which have as yet been subjected to 

 this mode of decomposition, is not very large ; yet, from their per- 

 fect analogy of composition with many others, there can be but 

 little doutit of the general extension of the principle. 



The clilorides of potassium, sodium, barium, strontium, and 

 calcium, being all thus decomposed, tlie bromides, iodides, and 

 fluorides of the same and all weaker bases, must probably act in 

 the same manner. The fluoride of calcium, has, in fact, been 

 found to do so, by experiment, hydnilluoric acid lieing freely 

 evolved. In the same manner, from the decomposition of the 

 sulphates, may be inferred that of the seleniates; from the sili- 

 cates, tliat of tlie borates. 



The apidicability of this simple mode of decomposition to the 

 explanati«Mi of a great variety of geological changes, is too evi- 

 dent to escape the attention of those conversant with that science. 

 In a future paper I hope to be able to give a more complete ac- 

 count of some interesting facts which have been observed in con- 

 nection witli this subject, and to verif)', by experiment, many points 

 which must at present be left to inference and conjecture. In 

 fact, although the existence of this law of decomposition was as- 

 certained in lS+2, yet it has only been within a few months that I 

 have been able to give much attention to its investigation, which 

 must be my excuse for the imperfect and hurried manner in which 

 it is now communicated. 



PROCEEDINGS OF SCIENTIFIC SOCIETIES. 



INSTITUTION OF MECHANICAL ENGINEERS. 



April 26. — At the quarterly meeting which took place in the theatre of 

 the Philosophical Institution, Birmingham, George Stephenson, Esq., 

 President, in the Chair, the following papers were read: — 



CYLINDER-BORING MACHINE. 



" On the FiUtin^-vp of Ci/liiiders for Locotnolive Engines, and a descrip- 

 tion of a Machine for Boriny them." By Mr. C. Beyer. 



In the absence of Mr. Beyer, Mr. Fothergill described the machine in- 

 troduced at the last meeting, but the consideration of which was not then 

 entered upon. [See JoHnis/. p. 88.] Its object is to attain a uniformity in the 

 make, bore, and general size of cylinders, so that, in the event of an acci- 

 dent, they may be replaced by spare ones. To accomplish tins difhcult t^sk, 

 the machine now de^^cribed was invented. The description of this ma- 

 chine, which would require diagrams to make it intelligible, is briefly 

 this: — The bed upon which it is placed is that of a common slide-lathe, 

 sufficiently long to carry a double set of driving-gear, and admitting of the 

 sufficient traverse of the boring-carriage. The boring-bar is supported by 

 three bearings, the former of which is stationary, and firmly fixed to the 

 bed, to resist the end pressure of the cut when boring : the latter are fixed 

 Upon the carriage, and travel with it aloni; the boring-bar. To cause the 

 boring-carriage to move edgeways, a train of wheels ilescend at the back of 

 the machine to give motion to the shaft, and are transfixed by means of a 

 feathered worm, to tlie worm-wheel and pinion, both of which move loose 

 upon a fast stud of the carriage ; this same stuil serving as h fulcrum for a 

 lever, carrying, upon two opposite projections, the intermediate pinions. 

 To hold the cylinders while boring, the top of the carriage is formed into a 

 kind of square panel, by means of two plates, planed on the Inside, and 

 fastened to the sides of the bearings, and two cross-stretches. These 

 latter are also planed upon their inner faces, and are secured to the sides 

 and top of the boring-carriage, and have holes bored in them when se- 

 cured in their places, by means of the bend on the bar, corresponding in 

 diameter to the turned projecting ends of the cylinder to be bored. This 

 arrangement is for the purpose of securing uniformity between the exter- 

 nal and internal surface, so that the cylinder be fairly perforated, without 

 the dangerous fault of thick and thin sides. 



Mr. Fothergill proceeded to explain the diagrams which accompanied 

 the paper, and remarked that, without offering any criticism on the machine, 

 which appeared to him to bo admirable for its purpose, he would merely 

 direct the attention of the members to the great advantages which such 

 an invention must confer on those by whom these cylinders were used. 

 Say, that one of those iu use split — by this machine they had the defect 

 supplied immediately. 



Mr. M'CoNNELLalso Lore testimony to the advantages of a uniformity of 

 cylinder. An accident occnred to one of the cylinders in use on the line 

 T>ith which he was connected. Au order was forthwith despatched to 

 Manchester, and in three days he had another, which fitted exactly the 

 place occupied by the first. 



ON THE FORMATION OF TEETH OF DRIVERS OF PIN-WHEELS- 



The Secretary read a paper, descriptive of " A Machine for Forming the 

 Teeth of J]7teels." By F. Bashforth, M.A., fellow of St John's College, 

 Cambridge. 



The paper was accompanied by a model. Referring to Prof. Willis's 

 demonstrations, that the proper form for the teeth of spur-wheels is a com- 

 pound of portions of epicycloids and hypocycloids, he remarked that no 

 self-acting inacliiuery had been applied to give those forms of metal wheels 

 when mounted on their axes. The principle of the invention submitted to 

 the Institution was the well-known one, that if the pins be supposed to be 

 mathematical lines, the proper forms of the teeth of the driver will be por- 

 tions of the epicycloids, described by a point in the circumference of the 

 pitch circle of the pin-wheel, when caused to roll on the pitch circle of the 

 driver. The tracer being replaced by a cylindrical cutter, this, as it re- 

 volves on its axis, will form with accuracy the interval between the two 

 teeth of the driver. By turning the wheel to be cut through the proper 

 angle, the interval between the next two teeth will be formed, and so on 

 till the whole be completed. He proposed that the pins should be formed 

 in two parts ; a solid cylinder surrounded by a tube of iron; and when 

 the tooth of the driver came in contact with the outer case of the pin, it 

 would revulve through a small angle, and thus all abrasion of the teeth of 

 the driver would be avoided. 



Mr. M'CoNNELL was unable to see wherein the model before them dif- 

 fered from the plan now in use. In fact, it was nothing more than the old 

 cog-and-drum plan. Probably the idea occured to the inventor without 

 any knowledge of the existing machines, and, if so, he deserved commen- 

 dation for his ingenuity. 



Mr. C'owPER could not entirely agree with Mr. M'Connell. The teeth, 

 by this machine, were made by a given mathematical rule. That was the 

 only self-acting machine he had seea that struck a real epicycloid. 



Mr. Fothergill was unable to see anything in the machine practically 

 diflerent to those longer in use. If, however, the inventor was an amateur, 

 great credit was due to him for the inventive ability he had displayed in 

 the model before them. 



CRADDOCK'S BOILER AND CONDENSER. 



Mr. T. Craddock, of Birmingham, read a paper " On /lis Improved 

 Boiler and Condenser — their Suitability for Extmding the Cornish Economy, 

 and Preventing Boiler Explosions." 



In submitting to the meeting the subject of this paper, it appears de- 

 sirable to call attention to the well-established practical data, from which, 

 by the Cornish system of generating and using steam, such economical re- 

 sults have been obtained. To this end, a very brief review of the various 

 laws, or principles, immediately bearing upon the subject, seems to be es- 

 sential for placing the matter iu its proper light before the meeting. For 

 this purpose, perhaps the classified mode is the preferable one. 



1. We have to do with the laws by which heat is transmitted from 

 hotter to colder bodies, and vice versa. These demand in our steam-boilers 

 and condensers an extensive surface ; and, as far as other circumstances 

 will allow of, that such surface be composed of thin metal. It is further 

 necessary, if we would produce the greatest economy in the generation of 

 steam, that the heat produced in the furnace be, to as great an extent as 

 possible, absorbed by the water ; this is best effected by a subdivision of 

 the gases by a slow draught, and by completely surrounding the combusti- 

 ble matter in the furnace by the water in the boiler. 



2. The hydrostatic laws require, in order to render high-pressure sleam 

 equally sate from explosion as low-pressure, that we diminish the sec- 

 tional area of the interior surface of the boiler, upon which the pressure 

 of the steam acts, in the same ratio as we increase its pressure. If we do 

 this, then the rending force, tending to burst the boiler, remains the sama 

 at whatever pressure the steam be generated. 



3. The laws relating to latent and sensible heat, when considered in 

 combination with large volumes of water, and subjected to the casualties 

 attending the steam-engine, suggests the diminishing the quantity of water 

 necessary in steam-boilers, as far as practical circumstancs will permit, as 

 one of the surest means of preventing destructive boiler explosions. The 

 importance which attaches to the suggestions these laws present becomes 

 apparent when we consider the effects in case of explosion, which such an 

 amount of sensible heat produced, as that contained iu the large volume of 

 water necessitated ia boilers of 60-horse-power, for instance, and of the 

 usual construction, as the sensible heat contained in so large a volume of 

 water would, supposing the pressure of the steam to diminish from 40 lb. 

 to 20 lb. per square inch, generate a volume of steam, at 20 lb. pressure, 

 equal to 30,000 cubic feet. Here we have a cause equivalent to the dif- 

 fusive and destructive effects exhibited in common and large boiler explo- 

 sions. The boiler to which this paper refers, reduces the danger from this 

 cause nine-tenths, though the steam be generated in it at a temperature 

 and pressure of 100 lb. per square inch. In this case we find the sensible 



