tion to the designing and structural work of the regular course, and thus be fitted to take up on graduating the profession of an architect. In the courses of Mechanical and Electrical Engineering a large proportion of the work is identical, and students in either course may in addition elect a considerable amount of special work in the other course, under the advice of the Faculty, as a substitute for the same amount of work in his own course.

EFFORTS are being made to persuade President Taylor not to leave Vassar College for Brown University. With this end in view a meeting of the Alumni decided to try to collect the sum of $2,000,000 for the endowment of Vassar.

IT is announced that Mrs. Julia J. Irving will retire from the presidency of Wellesley College in June of the present year.

DR. MYRON D. GREEN has been appointed lecturer on photographic chemistry in the University of Cincinnati. A yearly course has been established in the subject, including each week one lecture and one afternoon of laboratory or field work. Our universities are beginning to recognize the importance of thorough and exhaustive instruction in this special branch of chemistry.

AT a meeting of the electors to the professorship of pathology of Cambridge University, held on February 11th, Mr. German Sims Woodhead, M.D., Edinburgh, was chosen to succeed the late Professor Kanthack. The London Times states that Professor Woodhead is the eldest son of Mr. Joseph Woodhead, formerly M.P. for Spen Valley, and was born at Huddersfield in 1855. He was educated at Huddersfield College and at the University of Edinburgh. He first became a teacher in anatomy and then pathology, and carried on original investigations in pathology in the Minto-house School of Medicine, the University of Edinburgh, the Edinburgh Royal Infirmary, and the laboratory of the Royal College of Physicians, Edinburgh. For upwards of eight years he has held the post of Director of the Laboratories of the Conjoint Board of the Royal College of Physicians and of the Royal College of Surgeons. He was Assistant Commissioner to the Royal Com

mission on Tuberculosis, and his report was published in 1895. He has published a treatise on practical pathology, and, in conjunction with Dr. Arthur W. Hare, has published 'Pathological Myrology.' He has also written on bacteria and their products. He has held the office of President of the Royal Medical Society.

THE Balfour studentship of Cambridge University, of the annual value of £200, for original research in biology, especially animal morphol. ogy, has been awarded to J. Stanley Gardiner, M.A., Fellow of Gonville and Caius College, for three years from March, 1899. Grants from the Balfour Fund of £50 each have been made to J. S. Budgett, B.A., of Trinity College, in aid of his researches on the development of Polypterus, and to L. A. Borradaile, M.A., of Selwyn Hostel, in aid of the expenses of his proposed journey in company with Mr. Gardiner, the Balfour student.

AN examination will be held at Merton College, on June 27th and following days, for the purpose of electing to three open natural science scholarships, of which one will be at Merton College, one at New College and one at Corpus Christi College. The scholarships are of the value of £80 per annum, and are open to all candidates, including, we believe, those who are not citizens of Great Britain, whose age on July 3, 1899, will not exceed 19 years. The subjects of examination will be: (1) chemistry, mechanics and physics, or (2) biology. An English essay, and a paper in algebra and elementary geometry, will also be set to all candidates. Candidates will have an opportunity of showing a knowledge of higher mathematics.

DR. DOMENICO SACCARDO has been appointed professor of botany in the University of Bologna; Dr. Fleurens, professor of technical chemistry in the Conservatoire des Arts et Métiers at Paris; Dr. Natanson, of Vienna, assistant professor of mathematics in the University of Cracow, and Dr. Moritz Hoernes, assistant professor of prehistorical archæology in the University at Vienna. Dr. Bing has qualified as docent in chemistry in the University at Bonn, and Dr. Emden as docent in physics and meteorology in the Technical Institute at Munich.

timately with the supporter of combustion, and it is also well recognized that many explosions are due solely to very rapid combustion, yet it is only within comparatively recent times, and since manufacturing operations have come to be carried on upon a very considerable scale, that we have had it strongly demonstrated that ordinarily combustible solids might, when finely divided and mixed with air, give rise, on ignition, to most violent and disastrous explosions, and it seems especially notable that the first well demonstrated cases of this kind should have arisen from the apparently harmless operations attending the grinding grain, and the more particularly as flour is not looked upon as a very readily combustible substance when compared with other commonly used solids.

Among the many instances of this kind which we have now on record we will cite that which occurred on the 9th of July, 1872,* when the inhabitants of Glasgow were startled by the report of an explosion which was heard to a considerable distance and which was found to have occurred in some very extensive flour mills, the front and back walls of which were blown out, while the interior was reduced to ruins, and speedily enveloped in flame which destroyed the remaining buildings. Several persons were killed, and a number of others were severely burned, or injured by the fall of

masonry.

On May 2, 1878, a similar disaster occurred in the enormous flour mills in Minneapolis, but in this case it was observed that the explosion which originated in the Washburn mill was communicated by flame successively to the Diamond mill and to the Humboldt mill. As a consequence of these explosions, the walls of these mills, which were solid masonry, six feet thick at the base, were razed to the ground; sheets of corrugated iron roofing, two by six feet in * Abel, Roy. Inst., March 12, 1875.

area, were projected to a distance of more than two miles; a wooden building fifty feet from the center of explosion was burst open; stout plate glass windows one-fourth of a mile away were torn out bodily, sash and all, and projected into the street; an immense volume of smoke and flame was projected to an estimated height of six hundred to eight hundred feet, and finally persons by the edge of the adjacent river observed a displacement of water, producing a wave estimated to be eighteen inches high, before they heard the report of the explosion. The concurrent testimony of persons employed in the mills, and of the experts who were called, proved the absence in each case of any of the so-called explosive substances on the premises and that the boilers had not burst, and from the facts brought out the origin was conclusively traced to the striking of fire by a pair of mill-stones, through the stopping of the 'feed,' and the consequent friction of their bare surfaces against each other, with the result that the mixture of air and fine flour-dust surrounding the millstones became ignited.

This ignition alone would not suffice to develop any violent explosive effects; for similar ignitions which have been not infrequently observed in small mills, where they have been caused by the stones 'striking fire' or by the incautious use of a burning lamp near the millstones, or the mealspout attached to them, have not been attended by any serious results. But in an extensive mill, where many pairs of stones may be at work at one time, each pair has a conduit attached, which leads to a common receptacle called an exhaust box; into this the mixture of air and very fine flourdust which surrounds the millstones is drawn by means of an exhaust fan, which is sometimes aided by a system of air-blowThe fine flour is allowed to deposit partially in this chamber or exhaust box, and the air then passes into a second cham

ers.

ber, called a stive room, where a further quantity of dust is deposited. It follows that when the mill is at work, these chambers and the channels are all filled with an inflammable mixture of the finest flour-dust and air, and that the ignition of any portion of the inflammable mixture will result in the exceedingly rapid spread of the flame throughout the whole, and will thus develop an explosion. The violence of such explosions depends much upon the details of construction of the exhaust boxes and stive rooms, and upon the dimensions of the channels of communication; it must obviously be regulated by the volume of the inflammable mixture through which the fire rapidly spreads, and upon the degree of confinement. In the case of the catastrophe at Glasgow the production of a blaze at a pair of millstones was observed to be followed by a crackling noise as the flame spread rapidly through the conduits leading to the exhaust box upon an upper floor, and a loud report from that direction was almost immediately heard. Professors Rankine and Macadam, who carefully investigated the cause of this accident, report* that other flour-mill explosions which they had inquired into had been observed to have been attended by a similar succession of phenomena to those noticed upon this occasion. The bursting open of the exhaust box by a similar though less violent explosion, attended by injury of workmen, the blowing out of windows and loosening of tiles, appears to have taken place on a previous occasion at these particular mills. In the last and most disastrous accident, however, the more violent explosion appears to have been followed by others, the flame having spread with great rapidity to distant parts of the mills through the many channels of communication in which the air was charged with inflammable dust, resulting from the cleansing and sifting opera* Abel, Roy. Inst., March 12, 1875.

tions carried on in different parts of the building, and rapidly diffused through the air by the shock and blast of the first explosion.

In the experimental investigation of the Minneapolis explosion by Professor S. F. Peckham it was shown that compacted masses of flour which had become heated and charred ignited readily and smouldered, but were inflamed only with considerable difficulty, though the atmosphere of the conduit from the stones, through which a strong current of air is being continually drawn and which is filled with a dense cloud of very fine particles of flour heated to a maximum temperature of 140° F, could be inflamed with comparative ease. White-hot wires and glowing charcoal were incapable of producing this inflammation, and only burned the particles in actual contact with them, and the only means by which the mixture, in the best proportions, could be made to burn explosively was by contact with flame.

The danger in the process was found to arise from the friction of the stones heating the last portion of the grist that remained between them to a temperature sufficient to char it or to convert it into a substance resembling tinder, which would readily ignite from a spark produced from the stones striking together. Although this burning mass could not inflame the dust-laden atmosphere, it did ignite wood, which a strong draught of air readily forced into a blaze. Under the conditions described with a draught of air passing through the dry stones strong enough to convey the pellets of smouldering tinder into the wooden conductor an explosion was a necessary consequence.

Knowing the chemical composition of flour, we may calculate approximately the mechanical work which a given mass of flour can perform, and find that the con*Am. J. Sci. 16 (3), 301-306; 1878.

tents of an ordinary sack, when mixed with 4,000 cabic feet of air, will degenerate force enough to throw 2,500 tons mass to a height of 100 feet. If we now consider the many tons of flour there must have been in a mill such as the Washburn 'A,' where as much as 1,000 pounds of dust per day was collected from a single pipe, we can readily comprehend how such great destruction could be wrought.

It is to be regretted that the experts who duly considered all the circumstances concluded that, while, by suitable precautions, the frequency of these flour-mill explosions may be diminished and the extent of the damage inflicted may be very much restricted, the nature of the operations is such that these explosions cannot be altogether prevented.

Since mixtures of wheat-dust with air have proved to be so explosive, we should naturally expect that analogous solids would form similar explosive mixtures with air, and, as a fact, we have recorded explosions of oatmeal in the Oliver mill in Chicago, of starch in a New York candy factory,* of rice in rice mills, of malt dust in breweries, of spice dust in spice mills, together with numerous instances of sawdust explosions, the more prominent being those which occurred in the Pullman car shops and at Geldowsky's furniture factory in Cambridge, Mass., still we should scarcely look for an explosion from such a cause in a soap factory. Yet a violent explosion occurred in 1890, in a Providence soap-works, in which the finely powdered saponaceous substance known by the trade name of 'Soapine' was being prepared, and the Coroner held in his finding that the explosion through which such injury was inflicted was caused by the ignition of soapine dust. Experiments made in this connection showed that this substance will explode

*L. W. Peck, Explosions from Combustible Dusts, Pop. Sci. Month., 14, 159-166; 1878.

under certain conditions with more violence than flour and apparently with the production of more heat.

The most unusual case of dust explosions, however, with which we have met was that of finely powdered metallic zinc which occurred at the Bethlehem Zinc Works in 1854. At that time Col. Wetherill devised a plan for utilizing the 'blue powder' which is the finely divided metallic zinc that is deposited in the prolongation of the condenser by swedging the powder into blocks and piling these blocks one above another in a furnace where they were melted down and run into spelter. The workmen in charge sought to facilitate the process by feeding the uncompressed powder directly into the furnace, but on trying to do so an explosion followed the loading of the first shovelful, and with such violence that the workman was blown from the top of the furnace and the blade of the shovel was driven into the roof of the building.

In pharmacy and the arts substances have been made either knowingly or accidentally from mixtures of combustible substances and supporters of combustion which have given rise to accidents, such as those from the parlor match and the chlorate troches, or from sodium peroxide and sodium bisulphite mixtures, as in the Whitecross Street explosion,† and the latter class of mixtures are to be particularly dreaded as the chemical action and subsequent explosion may be incited not only by contact with fire, but also by contact with water. Cavazzi ‡ points out that mixtures of sodium nitrate and hypophosphite detonate on heating, while Violette § proposed to use a mixture of sodium nitrate and acetate as a substitute for gunpowder, and these are but a few among the many explosive mixtures which may be compounded.

*U. 8. Nav. Inst. 11, 774; 1885.

† J. Soc. Chem. Ind. 13, 198-200; 1894. Gaz. Chim. Ital., 1886.

Berthelot sur la force de la poudre (3) 2, 315.