1841.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



859 



between waves and breakers is very important, the former being an undula- 

 tion, the latter being accompanied with a translation of the mass, and capable 

 therefore of exerting extraordinary forces on the masses opposed to them. 



Some remarks were made on statements in another Section, respecting the 

 destniction to which the limestone of which the Plymouth Breakwater is ex- 

 posed from certain animals {Saxicava rugosa). These animals do not, how- 

 ever, meddle with granite, and probably timber payed over with hot tar would 

 resist their ravages, as animals of this nature seem peculiarly averse to the 

 smell of tar and similar substances. 



" On Fontis of Vessels." 



Mr. Scott Russell reported the progress made by " the Committee on Forms 

 of Vessels" during the past year. The object of the experiments is two-fold 

 —to advance our knowledge of the laws of resistance of fluids, — and to obtain 

 data for tlie practical improvement of the art of naval construction. Many 

 and expensive are the experiments formerly made on this subject. Unfortu- 

 nately, these experiments had been made with imperfect apparatus, or under 

 circumstances different from the conditions of bodies moving on the surface 

 of the water, 'or on solids of a form unsuitable to the formation of ships, or 

 on so small a scale as to render them unworthy of the confidence of the prac- 

 tical constructor. In the present series of experiments a more simple appa- 

 ratus was employed than in any former series of experiments. The forms of 

 body experimented upon were those of actual ships, or bodies analogous to 

 those in use : it was the object of the experiments to supply the actual de- 

 siderata of hydrodynamics and of practical ship building. The experiments 

 were made on vessels of every size, from models of 30 inches in length to 

 vessels of 1,300 tons. The experiments v\ere also made upon vessels in water 

 of variable depth and in channels of various dimensions, so as, if possible, to 

 embrace all the elements of the resistance. A minute description of some of 

 the apparatus was then given, along with some general illustrations ; but as 

 the experiments were still in progress, and to be continued during the follow- 

 ing year, no general statement of results was entered into at the present 

 meeting. It was expected that by the next meeting the whole would be con- 

 cluded. 



** On Captain Couch's Chock Channels" 



Mr. Snow Harris explained and illustrated, by a model and drawings, the 

 safety chock channel, for allowing the masts and rigging of vessels to be 

 easily disengaged when the masts are carried away. Many cases have occurred 

 in which, with the rigging and ordinary channels, the greatest danger has 

 been incurred, in consequence of not being able to get clear of wreck. The 

 ordinary channels may be blown up by the sea ; whereas, if made solid, on 

 Capt. Couch's plan, all danger from this source will be avoided, and the sailors 

 would be at once able to clear the vessel of any wreck. 



" On ArnotVs Stove, and the Construction of Descending Flues, and their 

 jipplication to the purposes of Ventilation." By J. N. Hearder. 



The general advantages of Arnott's stoves in economizing fuel, avoiding 

 smoke, and regulating the temperature, are well known ; but these stoves are 

 attended with some disadvantages, of which the danger of explosion, and im- 

 perfect ventilation, are the most serious. The liability to explosion, Mr. 

 Hearder considers to arise from the construction of the stove, in having the 

 door air-tight ; the only aperture for air being the valve aperture of the ash- 

 pit. The air so admitted is immediately decomposed, and nearly the whole 

 of its oxygen is abstracted, so that by the time it has passed up through the 

 fuel, and reached the upper chamber of the stove, it has not oxygen enough 

 left to support combustion. The heat evolved by the lower stratum of fuel, 

 acting upon the upper stratum of fresh or unignited fuel, liberates from it the 

 inflammable gas which it contains, and which also accumulates in the top of 

 the stove. A mixture is then formed analogous to the fire damp of coal 

 mines, ready for explosion whenever the requisite oxygen or degree of tem- 

 perature shall be present. Under these circumstances, should the door be 

 opened, a burst of flame outwards may be the result ; or should a puff of wind 

 down the chimney carry the mixture down through the ignited fuel, an explo- 

 sion may ensue. Other causes, such as the sudden shutting or opening of the 

 doorofan apartment, may occasion the downward draught and consequent ex- 

 plosion. Now carbiiretted hydrogen will not explode when the proportion of 

 the air to the hydrogen exceeds a certain limit, so that if air be supplied to the 

 top of the stove, so as greatly to preponderate over the hydrogen, the latter will 

 burn off in a flame at the moment of its formation, or be carried up the flue. 

 Mr. Hearder, therefore, proposes as a remedy, perforations through the lower 

 edge of the door, so that air may be admitted on a level with the top edge 

 of the fire brick, through which a constant in-draught of atmospheric air will 

 be insured, sufficient to obviate the evil. The heat evolved by the perfect 

 combustion of this inflammable gas, under these circumstances, will, he says, 

 more than compensate for the admission of cold air into the upper part of 

 the stove. The perforations just mentioned will also obviate, in a great mea- 

 sure, the w ant of ventilation. The author suggests a small rarefying appara- 

 tus, to be inserted in the vertical shaft connected with a descending flue. 



" Some Eaperiments showing the possibility of Fire, from the use of Hot 

 Water in vanning Buildings, and of Explosions in Steam Engine Boilers." 

 By Mr. Goldsworthy Gurney. 



After detailing several instances of fire which arose from the steam pipes 

 of water apparatus used for warming houses, the author proceeds to describe 

 some of the experiments likely to be of practical value. From a tubular 

 boiler, driving a high pressure engine, the injection pump was cut off — half 



an hour after the supply jjump was stopped, no water appeared on opening 

 the gauge cocks, and the engine was observed to slacken its rate and to move 

 sluggishly — it liad dropped from .^0 to 30 strokes a minute. The steam pipe 

 from the boiler to the engine was 40 feet long, and was carried for convenience 

 through the open air, thickly wrapped round vvith woollen cloth to prevent 

 radiation : soon after the engine became sluggish, the woollen cloth was ob- 

 served to char near the boiler, which soon extended along the whole length 

 of pipe ; the engine still working, but with more apparent difficulty, making 

 only 16 strokes per minute; Ihe pressure gauge, which usually ranged be- 

 tween 30 and 10 pounds, now stood at 15, and was gradually sinking. In 

 about five minutes after the woollen cloth had charred, a lead flange, used as 

 a parking at the cylinder joint, melted, and was followed by a loud escape of 

 elastic matter. The engine stopped working, and on bringing a lighted match 

 into the escapage, it took fire, and burnt with the lambent flame of hydrogen 

 gas. The author's imjiression was. that the escaping vapour was not pure 

 hydrogen. Water condensed on a piece of cold iron held in the flame, but 

 no water condensed on the cold iron after the flame was extinguished. On 

 examining the boiler, all the tubes were found red hot. This experiment was 

 repeated with many modifications. The temperature of the escaping vapour 

 was ascertained by means of bars, previously prepared to melt at different 

 temperatures; these indicated a temperature of about 400°. In about eight 

 minutes a piece of pure lead melted — -woollen cloth was charred, and a piece 

 of tow held in the esc.ipage took fire. In other experiments it was found, 

 that the pipes became sufficiently hot to exjdode gunpowder, and many che- 

 mical preparations. Having satisfied himself of this property of heated steam 

 or elastic matter, formed from the last portions of water in a boiler, the 

 author proceeded to examine, as far as possible, its chemical nature — to de- 

 termine whether any decomposition, or new elementary formation, took place, 

 He found that the clastic matter was not eoudensil)ie over cold water, and 

 would not in many cases burn, or show any indications of the presence of 

 hydrogen, or other inflammable matters. In some experiments it was found 

 it would extinguish flame. The experiments with copper vessels afforded the 

 same results as those manufactured from iron. From these experiments it 

 appeared, that whenever the heating apparatus falls short of water, the elastic 

 matter formed over the fire will carry sufficient heat through close pipes, to 

 any distance, to set fire to wood and other combustible bodies, and that 

 whether the hot water apparatus be under pressure or not, or whether the 

 heating surface be of tubes, plates, or cylinders. On the other hand it would 

 further appear, from some experiments enumerated, that in no case is there 

 danger when a given quantity of water is present. Mr. Gurney suggests, that 

 if both ends of the circulating series in hot water apparatus, namely, the part 

 which immediately goes from the heating surface beyond the furnace, and 

 that part where the circulation returns to it before it enters the furnace, was 

 made of a metal which would not melt at the fair working temperature of 

 the water, but which would melt at a temperature of from 5 to 600° of heat 

 (say lead pipe), there would be little, if any, danger from fire. 



It was mentioned that some experiments made many years since, by Woolfe, 

 on some of the boilers of the Cornish steam engines, corroborated the facts 

 now stated. It was also mentioned by Mr. Hunt, on the authority of Capt. 

 Tregaskis, that where the boilers had been covered with sawdust, it was found 

 in some instances, and in a very short time, to be charred. 



" Account of the Strata penetrated in sinking an Artesian Well at the ViC' 

 toria Spa, Plymouth." By Dr. Edward Moore. 



The author pointed out the mode by which the operations were conducted. 

 The strata penetrated were as follows : — Earthy clay slate, 20 feet ; lime- 

 stone, 150 ; blue slate, 20 ; red sandstone, 3 ; red slate, 37 ; limestone, 50 ; 

 sandstone, 4 ; red and blue slate, 30 ; dunstone, 8 ; earthy clay slate, 20 ; 

 red sandstone, 12 ; making a total of 305 feet. The earthy slates were of 

 the character of those generally found under the limestone, but they were in- 

 terspersed with blue shillat slates, similar 4o those which occur above it. 

 From the circumstance of the slate rocks immediately below the red sand- 

 stone being in each instance tinged red, the author imagined that their colour 

 might in these cases, if not in all, arise from the iron of the red bands affect- 

 ing them by percolation. He next remarked that from the alternations of 

 slate and limestone, the former appearing, from a consideration of the section, 

 to come up in wedges through the latter, it might be possible that the opinion 

 that some of the Plymouth Hniestones might have been formed in a manner 

 analogous to the modern coral reefs, was founded on correct data, although 

 in man; other localities in the vicinity the bands belong to the same unin- 

 terrupted series of deposits. The quantity of water obtained was at first con- 

 siderable, and overflowed the pipe ; at present it generally remains about two 

 feet below the surface, from whence it is carried to the saloon by a pump ; it 

 is clear and sparkling, and of a saline taste ; it has been examined by Profes- 

 sors Faraday and Daniell, and found to contain in the imperial pint S'lOO 

 cubic inches of carbonic acid gas, and 15166 grains of dry salts, thus: — 



Chloride of Sodium 9664 



Muriate of Magnesia 18'68 



„ „ Lime 1510 



Sulphate of Soda 9-55 



„ „ Lime 8-94 



Carbonate of Lime 2'06 



„ „ Iron 0-69 



151-66 

 Its specific gravity at 62° is I013'3. 



