Petroleum as a Substitute for Coal. --Some recent experiments with petroleum oil used for heating water, gave results from which it was estimated that petroleum had more than three times the heating effect of an equal weight of coal. Mr. Richardson's experiments at Woolwich, however, gave an evaporation of 13.96 to 18.66 lb. of water, by one pound of American petroleum; 9.7 lb. of petroleum being burnt per square foot of grate per hour. With shale oil the evaporation was 10 to 10.5 lb. of water per pound of fuel. The evaporative power of good coal may be taken, for comparison, at 8 to 8.5 lb. per pound of fuel. Taking into account the saving of freight due to the better quality of the fuel, and the saving of labor in stoking, it is possible that at some future time mineral oil may supersede coal in some of our ocean steamers.--
Frith of Forth Bridge. --Parliamentary sanction has been obtained for a bridge over the Frith of Forth, of a magnitude which gives it great scientific interest. It is to form part of a connecting-link between the North British and Edinburgh and Glasgow Railways. Its total length will be 11,755 feet, and it will be made up of the following spans, commencing from the south shore:--First, fourteen openings of 100 feet span, increasing in height from 63 to 77 ft. above high-water mark; then six openings of 150 ft. span, varying from 71 ft. to 79 ft. above high water level; and then six openings of 175 ft. span, of which the height above high-water level varies from 76 to 83 ft. These are succeeded by fifteen openings of 200 ft. span, and height increasing from 80 ft. to 105 ft. Then come the four great openings of 500 ft. span, which are placed at a clear height of 135 ft. above high-water spring tides. The height of the bridge then decreases, the large spans being followed by two openings of 200 ft., varying in height from 105 to 100 ft. above high-water; then four spans of 175 ft., decreasing from 102 to 96 ft. in height; then four openings of 150 ft. span, varying in height from 95 to 91 feet; and lastly seven openings of 100 ft. span, 97 to 93 feet in height. The piers occupy 1,005 feet in aggregate width. The main girders are to be on the lattice principle, built on shore, floated to their position, and raised by hydraulic power. The total cost is estimated at £476,543.--Engineering, Jan. 5.
Origin of the Diamond. --Contrary to the usual opinion that the diamond has been produced by the action of intense heat on carbon, Herr Goeppert asserts that it owes its origin to aqueous agency. His argument is based upon the fact that the diamond becomes black when exposed to a very high temperature. He considers that its Neptunian origin is proved by the fact that it has often on the surface impressions of grains of sand, and sometimes of crystals, showing that it has once been soft.
The Purification of Coal-Gas. --An important essay on this subject has been written by Professor A. Anderson, of Queen's College, Birmingham. It relates chiefly to the methods discovered by the author for the successful removal of bisulphide of carbon and the sulphuretted hydro-carbons by means of the sulphides of ammonium. By washing the gas with this compound, a very large proportion (nearly 35 per cent.) of the sulphur impurities are removed, and the illuminating power of the gas, so far from being diminished, becomes actually increased. Professor Anderson records several carefully conducted experiments, all of which prove the truth of the conclusions at which he has arrived. His method is now in operation at the Taunton and other local gas-works, and is highly spoken of by those who have given it careful consideration.
Paraffine in the Preservation of Frescoes. --In Dingler's Journal et Bulletin de la Société Chimique it is stated that paraffine may be used with advantage for the above purpose. Vohl coats the picture with a saturated solution of paraffine in benzole, and, when the solvent has evaporated, washes the surface with a very soft brush. Paraffine has this advantage over other greasy matters--it does not become colored by time.
Welsh Gold. --During the year 1864, we learn from statistics only recently published, there were five gold-mines working in Merionethshire. In these 2,836 tons were crushed, from which 2,887 ozs. of gold, valued at £9,991, were obtained. This is in excess of the quantity obtained in 1868, which was only 552 ozs.; but it is considerably less than the production of 1862, when 5,299 ozs., having a value of £20,390, were extracted.
A New Train-Signaling Apparatus.--Sundry mechanical contrivances and improvements in philosophical apparatus have been exhibited at the scientific gatherings of the present season in London, attracting more or less of attention, according to their merits and utility. Mr. Preece's train-signalling apparatus for promoting the safety of railway-travelling, can hardly fail of being interesting to everybody. It is in use on the South-western Railway, and if properly used, accidents from collision ought never to happen; it has the advantage of being applicable to any number of stations, which is of importance, considering how stations are multiplying in and around the metropolis. Mr. Preece has a very simple and complete method of communication between the signalman and switchman. The latter, on being informed that trains are waiting to come in, operates on the lever-handles before him, there being as many handles as lines of converging railway; and these handles are so contrived, that on moving any one to admit a train, it locks the others; so that if the switchman should pull at any one of them by mistake, he cannot move it. He is thus prevented from admitting two trains at the same time upon one line of rails, and thus one of the most frequent occasions of railway accident is avoided. And besides this, safety is further promoted by a series of small signal-discs, which start up before the switchman's eyes at the right moment, and give him demonstration that he has given the right pull at the right handle.
Action of Liquid Manure on certain Soils. --Some recent researches on this point, conducted by Professor Voelcker, were alluded to by Dr. G. Calvert in his Canton lecture before the Society of Arts. In some respects Dr. Voelcker's conclusions differ from those of Mr. Way. They are briefly as follows: (1.) That calcareous, dry soils absorb about six times as much ammonia from the liquid manure as the sterile, sandy soil. (2.) That the liquid manure in contact with the calcareous soil becomes much richer in lime, whilst during its passage through the sandy soil it becomes much poorer in this substance. (3.) That the calcareous soil absorbs much more potash than the sandy soil. (4) That chloride of sodium is not absorbed to any considerable extent by either soil, (5.) That both soils remove most of the phosphoric acid from the liquid. (6.) That the liquid manure, in passing through the calcareous soil, becomes poorer, and in passing through the sandy soil becomes richer in silica.
The Value of Sewage. --This important question, which has been so ably discussed by Baron Liebig in his various works upon Agricultural Chemistry, had a paper devoted to it by Dr. Gilbert at a late meeting (February 1st) of the Chemical Society. After entering into the details of his subject, the author draws the following general conclusions: 1st. It is only by the liberal use of water that the refuse matters of large populations can be removed from their dwellings without nuisance and injury to health. 2d. That the discharge of town sewage into rivers renders them unfit as water supplies to other towns, is destructive to fish, causes deposits which injure the channel, and emanations which are injurious to health, is a great waste of manurial matter, and should not be permitted. 3d. That the proper mode of both purifying and utilizing sewage-water is to apply it to land. 4th. That, considering the great dilution of town sewage, its constant daily supply at all seasons, its greater amount in wet weather, when the land can least bear, or least requires more water, and the cost of distribution, it is best fitted for application to grass, which alone can receive it the year round, though it may be occasionally applied with advantage to other crops within easy reach of the line or area laid down for the continuous application to grass. 6th. That the direct result of the general application of town sewage to grass land would be an enormous increase in the production of milk (butter and cheese) and meat, whilst by the consumption of the grass a large amount of solid manure, applicable to arable land and crops generally, would be produced. 6th. That the cost or profit to a town of arrangements for the removal and utilization of its sewage must vary greatly, according to its position and to the character of the land to be irrigated; where the sewage can be conveyed by gravitation and a sufficient tract of suitable land is available, the town may realize a profit; but, under contrary conditions, it may have to submit to a pecuniary loss to secure the necessary sanitary advantages.