526

mediate stage when the plant is from 4 inches to 5 inches high.

Dr. Henry followed with an account of the glucosides containing the hydrogen cyanide, which have been grouped together as cyanogenetic glucosides. They are allied to amygdalin, the active principle in bitter almonds, which is therefore the oldest known representative of the group. The list at present comprises, besides amygdalin, sambunigrin, prulaurasin and a glucoside, prepared artificially from amygdalin by Fischer, known as mandelnitrileglucoside, all of which are resolved by acids into glucose, benzaldehyde and hydrogen cyanide; further, dhurrin, phaseolunatin, lotusin and gynocardin.

The plants containing these glucosides also contain enzymes, which resolve them-when the plant is macerated with water-into hydrogen cyanide, glucose and a third constituent. The question was raised as to the rôle of the hydrogen cyanide, whether it acted protectively or whether it played a part in the production of proteid from nitrates. Dr. Greshoff, of Harlem, dealt with the question from the botanical side, and put forward a list of all the species of plants known to yield hydrogen cyanide, which will be of great value to future workers.

A paper on the utilisation of atmospheric nitrogen by plants, read by Mr. Thomas Jamieson, described what the author regarded as special organs in plants adapted for the direct absorption and assimilation of nitrogen from the air. His conclusions were most severely criticised by Prof. Potter from the botanical side, and by Mr. A. D. Hall and others.

The report on caoutchouc, presented by Mr. S. S. Pickles, contained a general survey of the chemistry of this remarkable product.

con

con

The methods and results of these workers were While Atwater's standard sidered and criticised in detail. was thought to be too high, it was generally agreed that Chittenden's values were too low. Voit's standard was accepted as the most probable.

Mr. Seebohm Rowntree's well-known experiments carried out in York were referred to, and it was pointed out that in studying actual dietaries of poor families averages were used in compiling statistics, a method which is open to criticism, as the bread-winner-owing to the self-denial of the woman-as a rule, gets far more than his share, so that the diet of the average working man is actually in most cases far richer in protein and has a greater energy value than is imagined.

Attention was directed by Dr. Hopkins-and this point was particularly emphasised by Prof. Armstrong-that it was not justifiable to consider merely the gross amount of protein, but that the nature of the protein had also to be taken into account. Thus, for example, wheat is probably not the best form of protein, its main constituent, glutaminic acid, being, so far as our present knowledge goes, of relatively little value as a tissue former compared with other amino-acids. Maize protein is perhaps of even lower value, whereas rice and oats, among the cereals, appear to be the especially valuable sources of protein. Prof. Armstrong particularly referred to the need of making detailed study of foodstuffs, our present method of referring to the nitrogen content generally multiplied by a factor as

foods, inasmuch as protein is a highly complex material, made of ever-varying units, the nutritive value of which taken singly varies within wide limits.

Prof. Karl Harries, of Kiel, in a communication read by Dr. Crossley, dealt with the products obtained by sub-protein giving no true guide as to the relative value of mitting caoutchouc to the action of ozone, and then distilling the ozonide with steam, viz. lævulinic aldehyde, lævulinic acid and hydrogen peroxide. Harries cludes that caoutchouc is a polymer of a 15-dimethylcyclo-octadien. Prof. W. A. Tilden described his observations on the behaviour of isoprene, prepared from oil of turpentine; when kept it gradually polymerises, being converted into a substance having many of the properties of caoutchouc. He also contributed a paper on the constituents of Dyera Costulata.

Mr. H. H. Robinson followed with a brief account of the chemistry of gums, dwelling especially on gums from India and the colonies which afford acetic acid when exposed to the action of moist air. He suggested that by partially hydrolysing the inferior Indian gums they might be made of greater industrial value. In the subsequent discussion, Mr. S. H. Davies stated that constitution had so far been found to have little bearing on the technical value of gums, viscosity being the quality chiefly required.

In his report, Mr. R. J. Caldwell collected and critically discussed the literature bearing on the hydrolysis of sugars, a subject of considerable interest at the present moment on account of its bearing on the theory of ionic dissociation and the nature of solution. Nearly 150 papers have been published on the subject, so that it is very difficult for a new worker in the field to acquaint himself with the literature. Mr. Caldwell has made a brief abstract of the essential points in each paper, and classified them in historical order under a number of appropriate subheadings. He sums up the evidence as to the nature of the change, and points out the unsatisfactory character of the argument based on the dissociation hypothesis that it is He is brought about by the hydrogen ions of the acid. inclined to believe that the facts are to be explained by an association hypothesis.

A large part of the morning of Tuesday, August 7, was devoted to a joint discussion with Section I (physiology) on the factors which determine minimal diet values. This was opened by Dr. F. G. Hopkins, F.R.S.; Prof. Dunstan and Prof. Armstrong spoke on the chemical side. It was generally agreed that the subject was of supreme importance, and one that should be attacked conjointly by chemists and physiologists. Dr. Hopkins dealt chiefly with the standards of minimal diets put forward by Atwater, Voit and Chittenden respectively. These incorporated in the following table :

are

The rest of the morning was devoted to agricultural chemistry, Messrs. A. D. Hall and C. T. Gimingham contributing a paper on the action of ammonium salts upon clay and kindred substances, following which Dr. E. J. Russell read a communication by Dr. F. V. Darbishire and himself on oxidation in soils and its relation to proan apparatus ductiveness. These authors have devised

for measuring the rate of absorption of oxygen; the power
of absorbing this gas possessed by all soils appears to be
due mainly, though not entirely, to the activity of micro-
organisms. The rate of oxidation does not entirely depend
on the amount of organic matter present in the soil;
moisture is essential, and as it increases so also does the
rate of oxidation. The rate is also increased by the addi-
For a series of
tion of calcium carbonate or of sugar.
similar soils, of which the cropping power is known, it is
found that the most productive has the highest rate of
oxidation, and that the others follow in the same order
for both properties. The parallelism holds also for soils
which have been artificially treated; it is essential, how-
The
ever, that the soil conditions should be aerobic.
authors suggest that the rate of oxidation affords
measure of the bacterial activity, which is closely connected
with productiveness.

a

The last paper read was by Mr. W. Popplewell Bloxam, on a new method of determining indigotin. After pointing out the need of a method of controlling the still very crude processes in vogue for extracting indigo, and the importance of determining the daily yield of indigotin obtained in an ordinary factory from known weights of green plant, the existing methods of analysis were discussed and the uncertainty of the results they afford alluded to. In the author's method, the indigotin is sulphonated by treatment with fuming sulphuric acid (containing 20 per cent. sulphur trioxide); the solution is then diluted, and the potassium salt of indigotin tetrasulphonate precipitated by means of potassium acetate. Finally, the amount of indigotin in the salt is estimated by titration with potassium permanganate or titanium chloride. The author concludes that the present process of manufacture is wasteful the highest efficiency attained not reaching 50 per cent., whilst on the average only 25 per cent. of the indigotin in the leaves is extracted.

a

one,

THE PHYSICAL GEOGRAPHY OF

VOLCANOES.

IN my discourse this evening I shall confine myself to that branch of vulcanology to which I have paid particular attention, viz. the naked-eye study of volcanoes

portions Atrio del Cavallo and Valle d'Inferno, while Vesuvius, the present active cone, occupies the southern part of the great crater which was formed by the destruction of that side of the Somma crater ring, probably in the Plinian eruption which destroyed Pompeii and Herculaneum in A.D. 79, or possibly in some earlier unrecorded

eruption. The observatory is situated on a projecting spur forming part of the old Somma ring, but separated from that mountain by a deep valley, the Fossa Vetrana, at the upper part of which took place the prolonged eruption which lasted from 1895 to 1898, and which built up a considerable hill, the Colle Umberto Io. Photographs of this place, taken in 1888, showed the scoriaceous or cindery lava of 1872, coulées of slaggy or ropy lava in 1898, a moving mass of scoriaceous lava and the growing cone in the same year, while a photograph of the latter, taken at night by the light of the incandescent lava streams themselves, excited much interest, and it was followed by another showing the same cone in 1906 covered, and its surface obscured, by a thick coating of ash from the last eruption.

In the Strombolian type of eruption the explosion takes place from more or less liquid lava, of which portions are hurled into the air, and by their rotation often assume pointed or even globular forms, which are permanently preserved by the solidification of the mass while in the air. In the Vulcanian type, the materials, which are affected by the explosion, being already solidified, the ejecta are chiefly fragmentary, varying from dust of microscopic fineness to "bread crust bombs" weighing several tons. The latter owe their name

FIG. 1.-Vesuvius from Cook's Eremo Hotel near the Observatory, April 26, 1906. Shows the
rounded top of the cone and the ash slides on it. Colle Umberto 1 in the foreground.

and their various constituent parts, their relations to one
another and to adjacent rocks and to other objects; how
they got to their present position and what effects they
produce; in other words, the physio-
graphy or physical geography of vol-
canoes. As this subject is itself too
large, I propose to take up the late
eruption of Vesuvius, alluding to other
volcanoes and their eruptions only by
way of illustration, comparison, or

contrast.

The south-east side of the Bay of Naples, which consists of the Sorrento Peninsula and the island of Capri, is a branch of the Apennine Chain; it consists largely of Apennine limestone of Cretaceous age, and is not volcanic. The north-west side of the Bay, on the contrary, is almost entirely volcanic. Thus the island of Ischia is subject to severe earthquakes, and contains Monte Epomeo, which has been twice in active eruption in historic times; the islands of Procida and Nisida contain craters; the Phlegræan Fields consist of numerous cones and craters, one of which, Monte Nuovo, was formed as recently as the sixteenth century. Moreover, Naples itself is built on volcanic strata. The whole district is subject to changes of level.

Coming now to Vesuvius, it is a matter of common knowledge that it consists of twin mountains, of which one, Somma, is part of an old

crater ring of gigantic size which no longer forms part of the working cone, which it partly surrounds, and from which it is separated by a great valley, called in different 1 Substance of a discourse delivered before the British Association at York on Friday evening, August 3, by Dr. Tempest Anderson.

to the characteristic crackings on the surface caused by the contraction of the crust when suddenly projected into the cold air, perhaps aided in some cases by the expansion of gases set free in the interior owing to the sudden reduction of pressure.

The Pelean type goes a stage further. In it a large proportion of the eruptive magma is blown to fine powder by the expansion of the gases it contains, and thus a mixture is produced of volcanic gases and incandescent dust in which each particle is surrounded and cushioned by an extremely thin layer of gas at a very high temperature, and therefore excessively mobile. The whole mass is therefore endowed with the mobility of a liquid, and under the influence of gravity rolls down slopes on which ordinary solids would lodge. This explanation of the hot blast which destroyed St. Pierre was first advanced by Dr. Flett and the lecturer in 1902, after witnessing an eruption of Mont Pelée, and it has since been generally adopted.'

In that year the Wallibu Valley at the foot of the Soufrière, in St. Vincent, was filled by such an incandescent avalanche to a depth of So feet, and the Rabaka Valley to a still greater depth. The torrential tropical rains, descending these valleys after the eruption, came in contact with this hot ash and caused various secondary phenomena, such as steam explosions, falls of ash, and gushes of boiling mud, which the lecturer compared with analogous, though somewhat different, phenomena during the late eruption of Vesuvius.

This eruption, as is usual with those of Vesuvius, presented features both of the explosive and efflusive types, i.e. explosions took place from the central crater, while a great fissure traversed the cone from north to south, and lava was discharged both to the north into the Atrio del Cavallo and also from, chiefly, three or four more bocce, or mouths, along the fissure to the south, which descended in the direction of Bosco Reale, Bosco Trecase, and Torre Annunziata.

The

The chief interest of the eruption of Vesuvius, however, undoubtedly centred round the explosions, the ejecta, and the secondary phenomena in connection with them. volcano was in unusual activity in April and May, 1905, and had never been absolutely quiet since that time. From April 4 to April 8, 1906, and to a less degree later, a series of explosions took place which enlarged the great central crater to an average diameter of more than a quarter of a mile (as measured by Prof. Loczy), removed the highest central part of the cone, and thus reduced the height of the volcano by about 350 feet, as measured barometrically by the lecturer's party. The resulting débris was distributed in part over the flanks of the cone, while a larger amount of smaller material was carried to the other side of Somma as far as Ottajano and San Giuseppe. In these villages it attained a depth of 3 feet to 4 feet, and broke down the roofs of many houses, and more than one church. In that of Giuseppe, about 250 persons, who had taken refuge, were buried by the débris and met their death. The crater as seen by the lecturer's party on two

ascents

was oval or heart-shaped, the longer diameter

streams and dark coloured ash; in April, 1906, it was thickly covered with whitish ash. This, when it attained a certain thickness, peeled off in veritable avalanches and slid down the mountain. The tracks present a radial appearance, and did so before any rain had fallen. It seems likely that the well-known umbrella-like markings on volcanic cones of tuff (consolidated ash), which have usually been attributed solely to erosion by rain, may in some cases, at any rate, be due to this cause. The avalanches were of sufficient power to carry away the Cook Railway. In one part below the funicular station the rails were bent like wire, and remained for a hundred yards or more along the sides of the avalanche track at right angles to their former position. They were kept together by their fish-plates, but had been entirely stripped of the sleepers. No stratification or particular structure in the materials brought down was noticed. A look out was kept for Lava del Fango (mud lava), which has often caused much damage after Vesuvian eruptions, but there had been no rain to form it before the lecturer's arrival, and comparatively little fell during his visit, so that only very small flows were seen. Prof. Lacroix, however, was fortunate enough to observe a large stream of mud above Ottajano, and he remarked that the resulting breccia was a little harder than the result of the dry avalanches, but presented no particular stratification or other structure by which it could be distinguished from the products of a dry avalanche of the same materials. Consequently no light is thereby thrown on the question whether many tuffs, such, for instance, as those which entomb Pompeii, were deposited, dry or wet.

Flows

The lava of this eruption also deserves mention. occurred from the north and south ends of the fissure through the cone above mentioned. That to the north flowed into the Atrio del Cavallo in the early part of the eruption. It was soon covered up with fragmentary ejecta. and at the time of the visit only a few fumaroles remained to mark the course of the fissure. On the south side of the cone three or four bocce, or mouths, opened along the fissure, the streams coalesced, and the lava flowed thus for more than half a mile. It then divided into branches, which to a large extent destroyed the villages of Bosco Trecase and Bosco Reale, and nearly reached Torre Annunziata. It crossed and filled up a cutting on the Circumvesuvian Railway.

The discourse concluded with a number of photographs of explosions from the crater taken by the lecturer during his stay of five nights at Cook's Eremo Hotel, near the observatory.

THE ASCENT OF RUWENZORI.

of September 13 some authentic details of the success of the Duke of the Abruzzi's expedition to Ruwenzori, from a letter received by him from Signor Vittorio Sella, who accompanied the expedition. Signor Sella wrote to Mr. Freshfield under date July 22, from Fort Portal:

being north and south, the walls sloping somewhat at the MR. DOUGLAS W. FRESHFIELD gives in the Times top, while lower down they were precipitous, especially towards the south side. At the north side the slopes were somewhat more gentle and the crater wider, while the lip was much lower, and broken down into a sort of plain some yards wide. This section of the crater corresponds exactly with a diagram in a report by the Academy of Sciences of Naples on the eruption of 1737. This eruption seems to have been very similar to that of the present year, and, as in this case, several persons lost their lives at Ottajano. There can be little doubt that the projection of fragmentary material in the direction of Ottajano was in both cases principally due to the shape of the crater when thus, so to speak, re-excavated. A.contributing effect was the south-west wind, which blew so strongly as to carry some of the finer material as far as Nola.

The

wind's effect was to be clearly seen in Naples, where several inches of dust were deposited.

The larger ejected blocks fell chiefly during the earlier part of the eruption on the slopes of the cone and round its foot, where they were mingled, and to a large extent covered up, with much ashes and scoriæ. Here were to be seen the most interesting phenomena of the eruption, viz. the great ash slides. The cone was previously almost smooth and very regular in outline. It consisted of lava

1 See Anderson and Flett, Phil. Trans., series A, vol. c., p. 353 et seq. (1903); also Anderson, Geographical Journal, March, 1903.

"His Royal Highness, accompanied by two Courmayeur guides, climbed all the five highest snowy peaks of Ruwenzori and took from them observations with a mercurial barometer besides a great many bearings with a prismatic compass. Captain Cagni carefully measured a base-line near Bujongolo in order to ascertain the exact distance between the highest peak of Kiyanja (which he climbed) and the rockshelter Kichuchu. His Royal Highness will therefore be able to publish a really good and complete sketch map of the snowy portion of the chain. Following in his Royal Highness's footsteps I ascended several high peaks and took many photographs and panoramas. I also secured many pictures in the forests and valleys of Mubuku and Bugiogo (the largest tributary of the Mubuku), and some telephotographs of the chain from near Butiti. The weather, however, was very trying to our patience. From June 12 to July 7 we had not a single really fine day.

THE TORONTO MEETING OF THE BRITISH margin for that reserve force " so necessary to ward off