while in the case of saturated steam the increased tension would be equivalent to about 27 millimetres.

From these experiments the Author deduces the conclusion that if the observed pressure is greater than that which would follow for the corresponding temperature from Regnault's law, the steam is mixed with air, and is not pure. If, again, the temperature is higher than the corresponding pressure, the steam is superheated, and only when the manometer indicates the required pressure coinciding with the observed temperature is the steam pure and saturated. It will not be surprising, therefore, if steam, which thus varies in its physical properties, varies also in its physiological action. The Author points out the practical bearing of these conclusions, and states that he is engaged in the construction of an apparatus, in which advantage is taken of the facts above indicated.

G. R. R.

On the Number of Bacteria present in the Soil.
By JOHN REIMERS, of Jena.

(Zeitschrift für Hygiene, 1889, p. 307.)

The previous investigations, which date from those undertaken by Birch-Hirschfeld at Dresden in 1874, are discussed, and reference is made to the importance of the discovery by Pasteur, in 1877, of the bacillus of malignant oedema, and in 1880 of that of anthrax in the soil. The first quantitative examination of particles of earth is due to Koch, who cultivated colonies arising from samples of soil in gelatin in 1881; but, as Fränkel has pointed out, his methods were imperfect. The plan of procedure adopted by Miquel and Adametz is also, as the Author shows, not to be depended upon. The investigations of Beumer, Maggiora, Smolenski, and Fränkel are in turn examined, and the Author lays down the following conditions for the successful solution of the question :(1). Everything that comes in contact with the sample of the soil to be tested must be perfectly sterilized; from the moment of its withdrawal from the earth, until it is shaken into the glass tube for gelatin-cultivation, the soil must be protected to the utmost extent possible from external impurities. (2.) Only absolutely fresh samples, and such as can be at once examined, are suitable. (3.) The investigation, based upon equal parts by volume, gives more reliable results than equal parts by weight; and (4.) The specimen of earth tested must be forthwith introduced into the gelatin, in order that, as far as possible, all germs may come under cultivation.

30

Instead of cubic centimetre employed by Fränkel, the Author used, as the tests, especially those from the deeper strata, based on a larger proportion of the soil, are obviously more trustworthy.

The prosecution of the drainage-works in Jena rendered it possible to obtain from the trenches, in course of excavation, reliable samples in all kinds of soils, at various depths, and thus to avoid the necessity of having recourse to borings, as had been the case in previous experiments. The plan adopted in making the tests was to reduce cubic centimetre of the soil, mixed with fluid gelatin in a sterilized agate mortar, to the finest possible state of subdivision. For the measurement of the sample a metal spoon was employed, which contained, after the particles of soil were perfectly levelled by means of the knife, which had been previously heated to redness, exactly cubic centimetre. The precaution used in filling the tubes and in estimating the colonies are described. The results of the various experiments on virgin soil outside the town, soil from beneath the roadways, from ground that had long been built over, from gardens, from land adjacent to factories, and from courtyards and cemeteries, are set forth in detail. In general the figures coincide more nearly with those of Fränkel than with the facts as given by other experimenters. The numbers of bacteria rapidly decrease in the deeper layers of the earth, both in the case of virgin soil, and in soil that has been polluted in various ways. The rapid decrease may be seen from the following figures:

Experiment 6

Depth below

Surface in
Metres.

Germs per
Cubic

Centimetre.
124,800

1

750

In Experiment 18 the decrease was very marked, even at 1 metre in depth; for while at the surface there were 432,400 germs, there were but 760 germs per cubic centimetre at a depth of 1 metre. In the cemeteries very similar conditions were found to prevail. The Author thus sums up his general conclusions on the whole subject:

(1.) The number of germs in the upper layers of the soil is by no means so great as many previous observers have stated. In the soil of this district (Jena), it never exceeds a few millions per cubic centimetre (7,600,000 in the worst case).

(2.) Up to a certain depth the number of germs remains relatively high, but always less than at the surface.

(3.) At increasing depths there is a tolerably sudden and marked decrease in the numbers, as Fränkel has already pointed out.

(4.) The zone of this sudden diminution lies in the Jena soil, as in that of Berlin, at a depth of between 1 and 2 metres.

(5.) The position of this zone would appear to depend chiefly upon the amount of superficial disturbance, and the mode of employment of the site in question. In made ground it lies deeper than in virgin soil.

[THE INST. C.E. VOL. XCIX.]

2 G

(6.) Even at quite moderate depths (2 metres) it is possible to find soil that is germ-free.

(7.) The same kinds of germs, in strata near the surface, show more vitality when under cultivation than those obtained from the deeper layers of the sub-soil.

Five other conclusions have reference to the action of the subsoil water; the pollution caused by interments, &c.

G. R. R.

The New Crematory at Zurich.

By A. GEISER. Stadtbaumeister.

(Schweizerische Bauzeitung, vol. xiv., 1889, p. 37.)

The disposal of the dead by cremation is not new, but of late the subject has been taken up with the view of dealing with it scientifically. On the crude method of burning the body in the open air on a funeral pile, the latest system here described, that of Mr. Emile Bourry, a French civil engineer, is a great advance. Both Venini, of Milan, and Siemens, of Dresden, have worked out systems, and have each erected a crematory. Venini, by means of the combustion of wood-gas, mixed with air, consumes the body by a flame impinging directly on it. Siemens puts the body into a furnace previously heated by gas, and admits to the furnace fresh air, which takes up the heat accumulated in the brick and ignites the body. Bourry, heating the furnace first of all by means of a coke stove, improves on Siemens' system, by using the heat developed in the combustion of the body itself to heat a cellular system, through which the feed-air is passed. Thus not only economy of fuel is obtained, but also in the time between any two cremations, as two or more may be consecutively carried out without waiting to re-heat the oven, which is necessary in Siemens' system. The preparatory heating, as also in Siemens' method, takes from eight to ten hours, the weight of coke being approximately 20 centners (about 1.94 ton), costing from 40 to 50 francs, but for a second or any following cremation only 2 or 3 centners more are required. The temperature of the furnace appears in every system to be about 700° or 800° Centigrade. Other advantages of the Bourry system are:-(a) The chimney from the furnace need be only 10 metres (33 feet) high, and is therefore concealed in the building; (b) the whole operation, from beginning to end, is carried out in full view of the relatives; even the actual combustion of the body in the furnace may be watched through a small opening. To preserve the outward semblance of burial Siemens uses a grave-like opening in the floor through which the body is lowered, and from which, unseen by the bystanders, it is moved into the furnace. Bourry, however, laying particular stress on every operation being visible, has the coffin placed on an iron table along which it is made to slide first

into an iron case, the door of which is then closed, and then, the door being opened, the body is slid into the glowing furnace. The actual time of burning occupies (for an adult) two hours without. and two hours and a half with, a coffin; at the end of which time a lever is moved actuating a kind of rake, which gathers the ashes to a funnel-like opening on one side of the front of the furnace, from which they fall silently into a small earthenware urn placed to receive them. The lid of this urn is then closed, sealed, placed in a larger funereal urn and delivered to the relatives of the deceased. The whole operation is noiseless and reverent.

The Zurich crematory was commenced in the autumn of 1887 and finished in the course of the following year. The façade is of Ostermunder sandstone, the base and steps being of granite. It consists of a large hall, 41 feet long by 23 feet wide by 24 feet high, containing the furnace, and adjoining to this two rooms, the one for waiting, the other for registration and storage of papers, each approximately 14 feet by 9 feet. The cost, exclusive of the land, which was the gift of the city, was £2,080.

The Paper is illustrated by scale drawings and photographs showing the exterior and interior of the completed building.

E. L. W. H. S.

Wery's Apparatus for heating Retort-Furnaces. By L. BRÉMOND. (Journal des Usines à Gaz, 1889, p. 153.)

The cost of fuel for heating retort-furnaces is a most important expense in the manufacture of gas. Various recuperative furnaces for utilizing the waste heat are known, likewise the non-conducting coverings of Le Treust and others, besides other means that have been proposed for economizing the fuel. It costs the Paris Gas Company 14d. for fuel for producing 35,300 cubic feet of gas, while the cost to many other companies is double that amount, and, in small works, the cost rises to as much as 98. 7d. per 35,300 cubic feet. These differences may be partly due to variations in the price of the fuel; the coke being, in some places, valued at the selling price, while others calculate it at a uniform and conventional rate. However this may be, considerable variations do exist in the quantity of fuel used for heating the furnaces, even in the best managed works of similar sizes, and the differences become enormous if small works are compared with large ones. It is therefore desirable to find a simple and inexpensive means for economizing fuel, applicable to all gasworks, and Wery's apparatus fulfils these conditions, effecting a saving of from 15 to 20 per cent. in the fuel.

On behalf of the Mechanical Arts Committee of the "Société d'Encouragement," Mr. Pihet has reported on Wery's smoke-consuming chimney, the principles of which are simply to mix a certain quantity of relatively cold air with the furnace gases in

the chimney; this is effected by the application of the principle of Giffard's injector; the air mixes with the hot gases in the chimney, passing through a circular orifice, reduced in section as much as possible, and proportional to the chimney. The current of cold air surrounds the furnace-gases in motion, mixes with them, lowers their temperature and diminishes the velocity of the draught. Without considering the theory of the principle, or determining whether similar results could be obtained by carefully regulating the dimensions of the exit orifice, Mr. Pihet found, from two carefully made experiments, that the Wery process was efficacious both for smoke-consumption and economy of fuel. He experimented with a 12-HP. portable engine and a tubular boiler without return flues or artificial draught. The consumption of smoke was perfect, and the economy of fuel, with Wery's apparatus, for an equal amount of work, and for the same quantity of water evaporated, amounted to 23 per cent.

Other trials were made by Mr. De Bange, General Director of the old Cail manufactory at Paris, with 20-HP. and 80-HP. engines, and with puddling-furnace and generator-furnaces: decided economy of fuel was found, and also a sensible reduction in the time required for getting up steam. With the steam-boilers, the saving was about 20 per cent., and with the puddling-furnace, in addition to the economy of fuel, the quality of the iron was superior to that obtained before using the apparatus. Mr. De Bange also made a trial to determine the quantity of water evaporated per pound of coal, with and without the apparatus, and found that the steam produced per pound of coal was increased by 28 per cent. by the apparatus.

Trials were also made at Denain by Mr. Jubeau with a puddlingfurnace on two steel ingots, each weighing about 4 tons, in two similar furnaces, the one with, and the other without the apparatus; these showed an economy of fuel of 16.79 per cent. in favour of the apparatus.

Other trials have also been made by Mr. J. Gaudry in the shops of the Compagnie Transatlantique, at Penhoet, which gave 10.2 to 10 7 lbs. of water evaporated per pound of coal with the apparatus as compared with 7.8 lbs. of water per lb. of coal without it.

As regards gasworks, the Wery apparatus produces a similar effect to that of Le Treust, which creates an intermittent draught in the chimney and drives the products of combustion back into the furnace when the register is closed. With the Wery chimney, vacuum and pressure are alternately seen, according to the condition of the fuel. No machinery or steam is required. It can be fixed to existing chimneys, but the most convenient plan is to construct a brick foundation and place the apparatus on it, surrounded by a sheet-iron chimney. An apparatus and chimney of a total height of 30 feet, and the chimney 114 inches diameter, was substituted for a brick chimney 62 feet high and 35 inches diameter; so that such large chimneys are not required, and the flames are not seen escaping at the top. At the small gasworks