oxygen, and only 45 litres of nitrogen, that is, oxygen practically pure for industrial purposes. To extract the gases, the authors employ a pump, and they tell us that if again exposed to charcoal, the oxygen will be obtained almost pure. There can be no doubt of it. They give no account of the cost of oxygen; but it is clear that it will be represented chiefly by the cost of the machinery and cost of working it. - Mec. Mag.

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THE SEWAGE QUESTION.

Among the best of the labored articles upon this subject we have perused is one entitled "A Chemist's view of the Sewage Question," by Edward C. C. Stamford, F.C.S., published in the Chemical News. Mr. Stamford clearly shows in his essay that the problem cannot be solved upon merely mechanical data. He says: The present water-closet system, with all its boasted advantages, is the worst that can be generally adopted, briefly because it is a most extravagant method of converting a molehill into a mountain. It merely removes the bulk of our excreta from our houses, to choke our rivers with foul deposits and rot at our neighbors' doors. It increases the death rate, as well as all other rates, and introduces into our houses a most deadly enemy, in the shape of sewer gases."

Mr. Stamford predicts that the water-closet will be ultimately doomed to oblivion. He reviews the process of Mr. Chapman, one of the latest proposed methods of dealing with town sewage, which is briefly a process of distillation, after treatment with lime and thorough putrefaction, points out important defects, and decides that its effectiveness is to say the least problematical. The process of Mr. Glassford, evaporation with sulphuric acid, he deems far more certain. But both these methods are connected with the water system, and this Mr. Stamford considers a radical defect.

The dry-earth system of Moule he considers the most hopeful of any yet proposed. The question of removal of sewage is not the only one that is to be considered; what to do with it after it is removed is the most puzzling part of the problem, and is strictly a chemical question.

The Moule earth system is the only one that has taken into full account the chemical bearings of the question and has dealt with it in a simple and practical manner. It at once provides for disposal and removal, making the former the prime object.

Mr. Stamford, in order to obviate a difficulty which seems to us purely imaginary, namely, the difficulty of obtaining a sufficient supply of pure dry earth, proposes to substitute seaweed charcoal, a powerful absorbent.

Now, so far as this is concerned we believe there will ultimately be no difficulty in obtaining earth for the purpose, but if the system should become general, the privilege of furnishing earth and taking away the resulting compost will be so valued as to make it a subject of solicitation; perhaps even a commercial

value will become fixed to the compost, and we may live to see the time when it will be found quoted in commercial price lists with guano and other fertilizers.

The amount of earth required is only 3 times the weight of the excreta, and as seaweed charcoal, though only one-fourth as much would be required, would certainly cost more than earth, the latter could never compete with the former except on shipboard, or in cases where large bodies of earth must be transported, unless the charcoal could be in some way renovated and its absorbent power restored.

As charcoal can be used over several times, and then redistilled with the mixed excreta, the whole ammonia product being recovered, and the charcoal thus renovated recovers its absorbent power, it may be that the system of Mr. Stamford will be found to possess some advantages.

Mr. Stamford has made some interesting researches on the products of the distillation of the mixed charcoal and excreta. These products are, he finds, remarkably similar in composition to the distillates from bones, in manufacturing boneblack. Ammonia, acetic acid, butyric acid, acetone, and pyrol are the most marked products, and the charcoal produced is, he asserts, second only in value to that of bones. The redistilled seaweed charcoal, and the charcoal resulting from the destructive distillation of the excreta, will give an increased weight of charcoal, so that, if this process were adopted, the product for the city of Glasgow alone, it is estimated, would be 19 tons per day.

The uses to which this charcoal might be applied are various. The system seems to have been the result of much study and close thought, but we doubt whether its merits will ever prove so great as to supersede the dry-earth method. - Scientific Ameri

can.

SALINE SOLUTIONS FOR STREET-WATERING.

The superintendent of street cleansing, etc., of Liverpool, has just issued his report to the Health Committee upon the trials made during the past season of Mr. Cooper's street-watering salts. The main thoroughfare along Lord, Church, and Bold Streets, chiefly macadamized, is considered to have afforded as severe a test as possible from the heavy traffic over it during the hottest period of summer. It is stated in the report that the use of these salts has been entirely successful, and beyond comparison superior to plain water. In practical results, two water-carts with the weak solution were found equal to seven under the old system upon the macadamized road; but in paved streets one may be expected to do the work of five where the traffic is only ordinary. Financially, notwithstanding the saving of horses and carts, it appears that, at the price of 3 pounds per ton, hitherto charged for the salts, no economy can be effected; but then the supply has been so far in experimental quantities, and it should be stated that the patentee. is now prepared to deliver in quantity at 40 shillings. It is further considered that a reduction of 70 per cent.

would be effected in water wasted in the streets, and that there is the collateral advantage of the surface of the roadways being maintained in superior condition, a saving of 20 per cent. in the cleansing being due to this effect. The system has also been tested in Greenock, and is reported upon equally favorably by Mr. Barr, C.E., the master of the works.

PEAT MANUFACTURE IN OHIO.

According to a writer in "Putnam's Monthly," for November, the following is the method employed in the manufacture of peat, near Ravenna, Ohio:

"The peat is dug to a depth of from 8 to 15 feet with shovels and slanes, the latter being a kind of spade, with a wing at the side bent at right angles with the blade, so as to form two sides of a square, and loaded into dump cars, which are drawn up, an inclined plane upon iron rails by friction gearing, and the contents rapidly emptied into an immense hopper containing 150 tons of crude peat. At the bottom of the hopper is a large elevating belt, running over drums, upon which the peat is thrown and rapidly carried into the condensing and moulding machine. Two men are all that are required to keep the machine full. The condensing and manipulating machine is run by steam power. It receives the crude peat from the elevating belt in a wet or moist state, and delivers it in a smooth, homogeneous condition, through 10 ovalshaped dies, each 34 inches by 4 inches in area, from which it is delivered on drying racks, passing horizontally under the machine. Each rack is 26 by 72 inches, constructed of light pine, holding 5 bars or canes of peat, which, when dry, will yield, to each rack, from 30 to 60 pounds of fuel, according to the density of the peat. The racks are carried from the machine on an inclined tramway made of light friction wheels, so that the racks will almost glide from their own gravity. These racks are taken from the tramway, and set up like an inverted V, on the drying-ground, where, being exposed to the sun, and the air circulating freely around and between the bars, they dry in from 10 to 12 days, and are ready to be loaded into cars for shipment and use. distance between the legs or base of the V being the same as their length, the drying ground is greatly economized. An acre will hold about 5,000 of these racks, from 15,000 to 20,000 being a requisite complement for the machinery. Sixteen men and 10 boys on the rackway will make 80 tons of prepared fuel per diem, indeed, there is hardly a limit to the capacity of the machinery, if labor enough is employed. With 37 men digging and clearing off the racks from the tramway, 150 tons of dried fuel can be made per day. This fuel can be delivered at a less price than the best coal, and the cost of preparing it for market is lighter than that required in coal-mining. It can be afforded as low as 4 dollars 50 cents per ton, and even lower, within a reasonable distance from the bogs, and it is more economical than coal.

The

"An analysis of the surface peat of this bog gives the following

result: carbon, 68 per cent.; oxygen, 18; water, 16; and ash 3.68 per cent. It also contains ammonia, acetate of lime, fixed and volatile oils. The deeper the peat found, the richer is it in carbon, and there are portions of the bog which will yield 70 to 75 per cent. of carbon. The average amount of carbon, thus far ascertained by analysis of the various peat bogs of the United States, equals 50 per cent."

HEAT IN MINES.

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The "Virginia City (Nev.) Enterprise says: The increase in the heat of our mines is now beginning to give many of our mining companies more trouble, and is proving a greater obstacle to mining operations in those levels lying below a depth of 1,000 feet, than any veins or 'pocket' deposits of water yet encountered. A number of the leading companies on the Comstock are now engaged in putting in engines to be used expressly for driving fans for furnishing air to the lower levels, forcing it through large tubes of galvanized iron. With this great increase of heat in our mines comes a great decrease of water; in fact, in our deepest mine- the Bullion, which has attained the depth of 1,200 feet-not a drop of water is to be seen; it is as dry as a lime-kiln and as hot as an oven.

"In the lower workings of the Chollar-Potosi mine, which are at a perpendicular depth of 1,100 feet below the surface, the thermometer now stands at 100 degrees, a frightful heat to be endured by a human being engaged in a kind of labor calling for severe muscular exertion. Here, also, we find the water to have decreased till there is at the present time a very insignificant amount, it being necessary to run the pump but 4 hours out of the 24.

"We might give other instances illustrative and corroborative of what we have stated, but deem the evidence afforded by two of our deepest mines, situated some considerable distance apart, sufficient. Does it not appear likely, judging from the present situation in the deepest levels of our mines, that the great Sutro tunnel, if ever constructed, is more likely to be found useful as a means of entrance for fresh air than of exit for water? The 'situation,' if we may so call it, so changes in our mines that we hardly know one month ahead what would be of advantage to us. Some months since we supposed we were to be drowned out of the lower levels of our mines, or rather prevented from ever attaining any very great depth, by a tremendous influx of water. Now we find no water at all- or at best a trifling quantity — but in its place hot air. No doubt this is a change for the better. It will be much easier to force a column of light and elastic air 1,000 feet downward than to lift a column of water the same distance.

"Should it prove a fact, as now seems probable, that the water in our mines is confined to certain strata at no great depth from the surface, say between the depths of 400 and 900 feet, and should it be found practicable to ventilate the deep workings of our

mines by forcing down air, some of our leading companies are likely to reach a depth much below the point where the Sutro tunnel will tap the lead before it is completed, even though work upon it should be at once commenced. Should the ChollarPotosi Company continue downward with their shafts at the same rate of speed that has distinguished their progress for some months past, they would, in less than two years, attain a point below that of the intersection of the Sutro tunnel with the Comstock lead. Whether another water stratum exists in the 800 to 1,000 feet of hot, unexplored region of rock lying between our present lower levels and that point on the lead which would be cut by the Sutro tunnel, no man can know."

VENTILATION OF MINES.

It having been asserted that the sole cause of the recent frightful destruction of life at Avondale, in Pennsylvania, was the use of a furnace for ventilating the mine instead of mechanical apparatus, we give some extracts from a paper which was recently read before the Institution of Mechanical Engineers, at Newcastle, England, by Mr. William Cochrane, and published in The "Engineer:"

"It is considered a fair estimate of the economic value of the average conditions in which furnaces are worked that only one fifth of the heat due to the combustion of the coal is utilized. There are many objections, besides the small useful effect, to the use of a furnace, which cannot be overcome, and which form a constant source of cost attendant upon it, namely, the necessity of cleaning the flues and the consequent suspension of the active ventilation of the mine; the inconvenience, and in some cases the impossibility, of using a shaft highly heated, and often full of smoke, for any other purpose than as a ventilating shaft; and the serious damage done by the products of combustion to castiron tubing, timber, pumps, or wire ropes, where winding is carried on in the upcast shaft, especially where the shaft is damp. If the conditions are unfavorable for the use of a furnace, such as shallow shafts and heavy resistances to be overcome, the furnace then is quite unable to compete with a good mechanical ventilator in economical effect. In a table compiled by Mr. J. J. Atkinson, Government Inspector for the Durham coal-field, has been shown the depth at which the furnaces are estimated to be equal to ventilating machines in point of economy of fuel, assuming that the sources of loss are of the same extent in each case, that is, the loss of fuel in furnaces by cooling in the upcast, and in ventilating machines utilized 60 per cent. of the engine-power. A recent calculation by M. Guibal, of Mons, deduces the following comparison: That if a furnace in a 12-feet shaft, 400 yards deep, circulate 53,000 cubic feet of air per minute under the total resistances represented by 3 inch water-gauge, and an average excess of upcast temperature of 108° above the downcast, with a duty of 31 lbs. of coal per horse-power in the air estimated on