tigations have thrown much fresh light on previously described specimens, besides furnishing some new species.*

One genus (Hylerpeton) Principal Dawson speaks of as "probably a somewhat clumsy creature of toad-like form and slow gait." It seems to have been armed with tusks, and to have lived on the landsnails (Pupa vetustata) that co-existed with it, for crushing whose shells its teeth were admirably suited. The Dendrerpetron, on the other hand, was "lizard-like in form, with a somewhat flat and broad head and strong teeth. . . . Its back was covered with a shining skin filled with microscopic horny scales."

Some remarkable shell-heaps, or "Sambaquis," are to be seen along the coast of Peru, composed of accumulations of either whole or broken shells. These mounds are occasionally 60 metres high and 100 metres in diameter; they lie either along the modern seaboard, or an old coast line now eighteen to twenty miles inland. Many of them, especially those formed of entire shells, are, like the Danish kitchen-middens, the result of human agency, and when cut through vertically exhibited the remains of fires, the bones of fishes and birds (chiefly parrots), and broken stone axes. Some true "burying-places" were also investigated, and found to contain entire human skeletons and well-preserved weapons and stone mortars of finest workmanship. Their explorer, Professor C. Wiener, considers that in this part of America the period of polished stone implements was prior to that of the chipped ones.†

An English translation of a well-known foreign work has just been brought out. "The Primæval World of Switzerland" was first published in 1865, at Zurich, under the title of "Die Urwelt der Schweiz;" a French edition being issued in 1872. The popularity which it so justly attained rendering an English version desirable, it has at length been translated by Mr. W. S. Dallas, Assistant-Secretary Geol. Soc. London, and new matter added, bringing it up to date. In it will be found a most interesting and entertaining account of the geological history of Switzerland; from the coal period, with its wonderful assemblage of plants, and including amongst its insect fauna cockroaches of a size calculated to make the modern house pest look

*Amer. Four. of Science and Arts, Dec. 1876.

+ Four. Imp. Geog. Soc., Vienna, 1876, pp. 486-9, and Geol. Mag., Jan. 1877.

small, down to that of the Swiss lake pile-dwellings and prehistoric man. Abundantly illustrated, the work cannot fail to interest all, especially those who have, or may be intending to visit this charming

little country.

At the anniversary meeting of the Geological Society of London, held on the 16th of February last, the usual yearly award of the medals and funds took place. The Wollaston gold medal was accorded to Mr. Robert Mallet, F.R.S., so well known for his researches in vulcanicity; the proceeds of the Wollaston fund were bestowed on Mr. Robert Etheridge, jun., F.G.S., of the Scotch Geological Survey. The Murchison medal was conferred on the Rev. W. B. Clarke, F.R.S., who has done so much to increase our knowledge of the geology of Australia; the balance of the fund being given to the Rev. J. F. Blake, F.G.S. The Lyell medal found a most worthy recipient in Dr. Hector, F.R.S., Director of the New Zealand Geological Survey; Mr. Pengelly, F.R.S., under whose directions the Kent's Cavern at Torquay is being excavated, receiving the balance. The first award of the Bigsby medal formed a new feature in the proceedings, and the Council of the Society have certainly done well in assigning it to Professor O. C. Marsh, of Yale College, New Haven, U.S., whose researches into the fossil vertebrate fauna of that country have been often alluded to in these pages. The presidential address which then followed must be reserved till our next notice.

TECHNOLOGY.-BY CHARLES W. VINCENT, F.R.S.E., F.C.S.

SPON

PONTANEOUS Combustion of Coal in Ships.-In 1874, the Board of Trade decided to hold no more inquiries into casualties caused by explosion or fire in coal-laden vessels, for the reason that the finding of their courts, which invariably took the form of an exoneration of the ship's officers, and a recommendation in favour of better ventilation, appeared to be entirely disregarded both by shipowners and underwriters. This determination led to the appointment of a Royal Commission of eminent scientific men and others, whose report, lately issued, goes far to justify the neglect with which the recommendations of the Board of Trade had been treated.

From the information collected by the Royal Commission it appears that the export of coal from the United Kingdom is as a whole steadily increasing, but that the export to distant and tropical ports is decidedly decreasing. The export to Africa, Australia, the East and West Indies, and North and South America, which increased by 14 per cent. in 1874, had decreased by nearly 7 per cent. in 1875. There is every reason to believe that this diminution in the amount of exported coal was mainly due to the large number of fires which occurred in 1874 on board coal ships bound for long voyages, particularly in the case of vessels with large cargoes. The return shows that, excluding the European trade, there were in 1874, 2,109 shipments with cargoes under 500 tons, in which five fires occurred, or under per cent.; 1,501 shipments, with cargoes between 500 and 1,000 tons, in which 17 casualties occurred, or over I per cent.; 490 shipments, with cargoes between 1,000 and 1,500 tons, in which 17 casualties occurred, or 34 per cent.; 308 shipments, with cargoes between 1,500 and 2,000 tons, in which 14 casualties occurred, or over 4 per cent.; 77 shipments, with cargoes over 2,000 tons, in which 7 casualties occurred, or 9 per cent.

The accidents in vessels bound to San Francisco were the most remarkable: deducting vessels under 500 tons (in which no cases of spontaneous combustion were recorded) the return shows 9 fires out of 54 shipments. These also increase in proportion to the tonnage of the cargoes, till the alarming fact is arrived at that out of the 5 ships with cargoes of over 2,000 tons, 2 suffered. It appears that these accidents occurred through no carelessness or want of precaution on the part of the officers and men of the ships, but were produced by causes of which they were ignorant, and from which in consequence they were unable to defend themselves.

What these causes were has been the subject of careful investigation, and the Commissioners have at length reported that the main conclusions they arrive at are as follows:—

That certain descriptions of coal are intrinsically dangerous for shipment on long voyages.

That the breakage of coal in its transport from the pit to the ship's hold, the shipment of pyritic coal in a wet condition, and, especially, ventilation through the body of coal cargoes (no wonder the inquiries of the Board of Trade proved abortive), conduce to spontaneous

combustion, even though the coal may not be unfit for conveyance on long voyages.

That the temperature of the various portions of the cargo should be tested periodically by thermometer; and that with a view to guard against explosion, free and continual egress to the open air should be provided for the explosive gases, by means of a system of surface ventilation, which would be effective in all circumstances of weather.

The reasoning upon which the above conclusions are founded is well demonstrated in a supplementary paper by Professor Abel and Dr. Percy. They show that the so-called spontaneous development of heat which occasionally takes place in coal, is due to chemical changes occurring through the agency of atmospheric oxygen upon iron pyrites (and possibly some other combinations of sulphur), and upon some carbo-hydrogen compounds forming part of the coal itself, which are readily oxidisable. Iron pyrites is of almost universal occurrence in coal. In some coals it is so distributed as not to be detected by ordinary inspection; in others it is in the form of more or less conspicuous laminæ, of a brass yellow colour; occasionally small distinct crystals of cubical form and bright metallic lustre are observed, and not unfrequently it is found in nodules (known as "brasses") and layers of considerable dimensions.

Pyrites vary greatly as regards their stability, or their liability to undergo oxidation by contact with the atmosphere. Some, after remaining unchanged during long periods of exposure, will undergo oxidation without any immediately apparent cause. Others are perfectly stable; and with others oxidation follows with more or less rapidity upon their exposure to the atmosphere. The presence of moisture promotes this oxidation; it does so apparently by bringing the atmospheric oxygen into more intimate contact with the surfaces of the oxidisable material. Similarly, the absorption of moisture by mineral substances of laminated or porous structure, through which pyrites are disseminated, promotes the oxidation of the latter by bringing the atmospheric oxygen, which is dissolved by the water, into more intimate contact with the oxidisable material. Thus the oxidation of pyrites in alum schist is greatly accelerated by occasionally watering loose heaps of the mineral, which are piled in such a manner that access of air to the interior can be regulated.

The oxidation of pyrites, as in most cases of chemical action, is accompanied by the development of heat, which may accumulate to such an extent as to lead to the ignition of the highly oxidisable constituents of the mineral through which it is distributed; the heaps of alum schist frequently take fire, and in the same way coal may become heated to, the point of ignition by the oxidation of the pyrites disseminated through it, if favoured by the presence of moisture and mechanical conditions favourable to the accumulation of heat.

This danger has become the greater of late years from the difficulty experienced in obtaining lads to clean the coal, i.e. to pick out the "brassy" pieces. Besides this, the men have been getting more careless in every way since wages were increased, and have been sending to the pit mouth inferior and unclean sorts, which formerly they would have been fined for digging out. Mr. Cooper Rundell, of the Liverpool Underwriters' Association, is of opinion that to these causes the greater part of the fatalities of 1873 and 1874 is due.

Another possible cause of the spontaneous combustion of coal is the absorption or condensation of oxygen within its pores. It is well known to chemists that this is a property of carbon in a finely divided state. Thus, wood charcoal which has been recently produced, or which has been freshly heated sufficiently to expel moisture and gases which it may have absorbed, will condense within its pores more than nine times its own volume of oxygen, and seven times its own volume of nitrogen, by simple exposure to the air.

The condensation of a gas by a porous body is attended by development of heat proportionate to the extent of that condensation. Moreover, the tendency to oxidation which carbon possesses is favoured by the condensation of oxygen within its pores, on account of the very intimate contact between the molecules of the two bodies. Hence the development of heat and the establishment of oxidation occur simultaneously; the latter is accelerated as heat accumulates, and chemical action is thus promoted, and may in course of time proceed so energetically that the carbon or carbo-hydrogen particles may be heated to ignition.

A good illustration of this action is afforded by the very porous