1843.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



305 



on obscured grounds. The improvement in the process of obscuring glass, 

 consists in mixing the materials, which are used to produce this effect, with 

 boiled oil, and transferring impressions from engraved metal plates on to 

 the glass j thus producing obscured patterns on transparent grounds. — Lon- 

 don Journal, 



PREPARING PAINTED SURFACES OF PAPER. 



Henry Martin, of Norton-terrace, Camden-town, painter, has obtained 

 a patent for " improvements in preparing surfaces of paper." — Patent 

 dated March 30, 1840. This invention consists in embossing and enamel- 

 ling the surfaces of paper, and in manufacturing paper-hangings. A coat of 

 oil-paint, of the desired colour, is first applied to the surface of the paper, as 

 evenly as possible, with a common paint-brush ; it is then rubbed lightly 

 over with a brush, similar to a clothes or shoe-brush (giving it a circular 

 motion), to remove the marks of the paint-brush ; after which, an addi- 

 tional smoothness is given to the painted surface, by passing a dry brush, 

 called a " softener," lightly over it. If more than one coat of paint be laid 

 on, this process is repeated. Or, instead of the above method, the paint 

 may be applied by conducting the paper between two rollers, together with 

 an endless felt or other fabric, which is supplied with paint by passing under 

 a roller partly immersed in it, the superfluous paint being removed from the 

 felt, as it ascends, by a scraper. The paper, thus prepared, is embossed, by 

 passing it between engraved rollers or dies ; or is converted into paper- 

 hangings, by printing the required designs upon it with blocks or other 

 surfaces. If a glazed or enamelled surface is to be given to the paper, the 

 oil-pp.int must be used in a thick or round state, and thinned only with tur- 

 pentine, in the same manner as if it were used for " flatting." When the 

 turpentine evaporates, the colour becomes set ; the paper is then placed 

 upon a bed of woollen cloth or other soft material, and a pallet- knife or 

 trowel, with a polished surface, is passed over the painted surface of the 

 paper, with a slight pressure ; the eolour being set, yields to the pressure, 

 and a glaze is thereby produced, which may be afterwards heightened in the 

 usual manner. Other means may be resorted to for glazing the painted sur- 

 face of the paper, if preferred. — London Journal, 



NEW SAFETY VALVE FOR ENGINE BOILERS. 

 (From the Transactions of the Liverpool Polytechnic Society.) 



The Secretary read an interesting letter on this subject from Mr. Maitland, 

 formerly a member of the society. It was dated Montreal, where the 

 writer was then residing. The following are extracts : — 



" Shortly after my arrival in this country, a serious explosion took place of 

 a steam-boiler on a canal high-pressure boat. The boiler was constructed on 

 the locomotive principle. The effect of the explosion took place immedi- 

 ately behind the tube-plate of the fire-box. The boiler had no appearance 

 that indicated that the explosion had taken place from scarcity of water. 

 The engineer, in evidence, declared that he was allowed to carry 85 lb., but 

 there is no doubt but that a much greater pressure than that would be re- 

 qiiired to tear the boiler in the manner the Shamrock's was torn. The 

 boiler was constructed throughout of -r-inch plate. This, there is no ques- 

 tion, is too thin for tube plates. The tubes were wrought iron. From 

 all the circumstances of the case, I have no doubt but the boiler 

 exploded from a too great accumulation of steam, and having either 

 a too small or inefficient safety-valve, they did not allow it to blow off. 

 From this circumstance I was induced to pay some attention to, and, if pos- 

 sible, to improve, the safety valve. I send you a sketch of one which I con- 

 sider does away with many of the objections of the present one in use. It 

 is more especially useful when steam of high pressure is used. If a valve is 

 constructed to be out of the reach of the engineer — that is, to be loaded in 

 the box that contains the valve, if the valve be of any size at all — the weight 

 requires to be enormous, for the pressure is 15, 20, or 30 lb. per inch. Iu 

 the valve I have invented this objection does not hold, as the same amount 

 of weight will load a 10-inch valve at the same pressure, as it would load on 

 the old plan a valve of 2 in. diameter. The top valve is 10 in. diameter, and 

 the lower one 9f inch; consequently, the area to be loaded is only a ring 10 

 inches diameter and one-eighth inch broad. As the Polytechnic Society is 

 established for the advancement of science, I will, if it would be of any 

 service to its members, prepare a paper on marine engineering in this country. 

 The boats attain a speed here, with an economy of fuel as you have as yet 

 not got at home. A boat was started this summer on the St. Lawrence, 

 called the Montreal ; she is the fastest in North America. Some engineers 

 visited her here from the Hudson, and they declared they had nothing that 

 surpassed her. She is 250 feet long; breadth, or beam, 27 feet; depth of 

 hold, 10 feet; diameter of cylinder, 57 inches; length of stroke, 10 feet; 

 diameter of wheel, 30 feet; length of float, 10 feet; and depth of float, 

 2 feet 6 inches; strokes, 21 per minute; steam, 25 lb.; speed, 15 miles per 

 hour !" 



Mr. Maitland's valve consists of a very simple and ingenious modifica- 

 tion of the common equilibrium valve, now well-known and much used 

 among engineers. Steam from the boiler enters freely a flat chamber, the 



top and bottom of which are formed by two valves, firmly connected 

 together and both opening upwards. Now if these two valves be of equal 

 diameter, the steam-pressure above the lower valve will exactly counter- 

 poise the pressure beueath the upper valve, consequently the valves will have 

 no tendency to rise, and no steam will be allowed to escape. But if we 

 suppose the upper valve to be even one-eighth of an inch the larger in diame- 

 ter, the pressure on it will overcome that on the lower valve, and the two 

 valves being connected together they will both rise, and allow the steam 

 rapidly to escape (upward through the upper valve, and downward through 

 the lower one) ; and it is evident that the weight necessary to load this 

 valve is exceedingly small, viz., just sufficient to balance the pressure on an 

 area equal to the difference between the areas of the two valves, whilst the 

 valve is as efficient as a common safety-valve having an area equal to the 

 sums of the areas of the two valves. The force necessary to keep this valve 

 down is so small that the ordinary lever is dispensed with ; and in place of 

 it a weight corresponding to the pressure required is placed immediately 

 upon the top valve, thus preventing a tendency to gag or stick from want of 

 attention, and making the apparatus what it really is — pre-eminently a 

 safety-valve. 



THE SMOKE NUISANCE. 



REPORT OF THE PARLIAMENTARY COMMITTEE. 



The select committee appointed to inquire into the means and the expe- 

 diency of preventing the nuisance of smoke arising from fires or furnaces , 

 and who were empowered to report their opinion, together with the minutes 

 of evidence taken before them, to the House, have considered the matters to 

 them referred, and have agreed to the following report : — 



In their endeavours to investigate the subject, your committee have 

 deemed it expedient to call before them a variety of persons. They have re- 

 ceived the evidence of the most eminent men in the science of chemistry, of 

 practical engineers of high reputation, of leading master manufacturers and 

 proprietors of steam-engines, and of ingenious persons who had devised 

 means and taken out patents for the prevention of smoke. The attention of 

 the parties called to give evidence has been principally directed to the con- 

 sideration of the following heads, on which their opinions were given. 



1. Whether it was practicable entirely to prevent, or very much to 

 diminish, the nuisance now so severely felt in large towns and populous 

 districts from the smoke of furnaces or of steam-engines. 



2. Whether, if this were practicable, it would be advisable to take any 

 steps to prevent the nuisance; as so doing might interfere with the pro- 

 perty or interests of manufacturers, or of the proprietors of furnaces. 



3. If, in the event of the two former questions being answered in the 

 affirmative, they would recommend some legislative enactment to be framed 

 to prohibit the nuisance of smoke. 



In regard to the first of these questions, it appears from the whole of the 

 evidence of scientific and practical men, including master manufacturers, 

 that smoke, which is the result of imperfect combustion, may in all cases be 

 much diminished, if not entirely prevented. 



It appears to be the unanimous opinion of the witnesses conversant with 

 the subject, that imperfect combustion arises from a deficiency of atmo- 

 spheric air to mix with and act on the inflammable matter at a proper 

 temperature, and under circumstances which must ensure its effective opera- 

 tion ; that this admission of air, properly regulated, is the great, if not the 

 only, principle of preventing smoke which is generally applicable; and that 

 all inventions for the prevention of smoke (except where the smoke has been 

 separated mechanically by an artificial shower of water, produced in a flue 

 constructed for the purpose,) are only various applications, in different forms, 

 of this general principle : even the flow or jet of steam which has been 

 applied by some persons to prevent smoke in furnaces, being merely a modi- 

 fication of this general principle ; as, though steam may modify combustion, 

 air must necessarily flow in with it, otherwise the combustion in the furnace is 

 arrested. 



The evidence before your committee further shows, that the admission of 

 atmospheric air, under proper regulations, into the furnace, is productive of 

 saving in fuel, by causing the particles of carbon, which would otherwise 

 rise in smoke and be wasted, to ignite, and thereby to increase the heat in 

 the boiler. 



It appears that the expense attendant on putting up whatever apparatus 

 may he required to prevent smoke arising from furnaces is very trifling; and, 

 as some of the witnesses observed, the outlay may be repaid within the year 

 by the diminished consumption of fuel. F'or additional information on this 

 subject your committee beg to refer to the evidence. 



Several most ingenious patents and inventions for the prevention and con- 

 sumption of smoke, were laid before your committee, which, from the testi- 

 mony of the proprietors of furnaces by whom they were adopted, appeared 

 to answer the twofold purpose of preventing smoke and of lessening the 

 quantity of fuel required. 



The means of preventing smoke might also be applied to the furnaces of 

 steam boats; but such application would be attended with rather more 

 expense than on land, from the occasional want of space, and the setting of 

 boilers, in a steam-vessel. No doubt, however, existed, in the opiuions of 



