April 27, 1899] 



NATURE 



619 



Since the publication of my paper in 1895, I have made a few 

 observations of interest to which I may now refer. Crystals of 

 saccharin which, when freshly prepared, flash brilliantly on 

 crushing, gradually lose this properly, and after a few weeks' 

 preservation show no appreciable triboluminescence. Further, 

 in order to obtain crystals which exhibit a brilliant tribolumin- 

 escence, the impure commercial saccharin must be crystallised 

 from acetone ; a carefully purified specimen of saccharin, when 

 crystallised from acetone, yielded crystals which do not phos- 

 phoresce at all when broken. Both of these points are of great 

 importance as affording possible clues to the cause of this strange 

 property ; it would be of interest to ascertain whether the tribo- 

 luminescence of cane sugar, hippuric acid, and other substances 

 is in any way characteristic of the freshly prepared crystals, and 

 is dependent on the presence of traces of impurity. Another 

 point of great interest, indicating that triboluminescence is 

 probably not a property of the chemical molecules, but only of 

 the crystalline structure, is noted in Brugnatelli's paper ; 

 although the crystals of dextro- and la;vo-ethylic santonite show 

 brilliant triboluminescence, the anorthic crystals of the racemic 

 compound of these two substances exhibit no triboluminescence. 



In concluding this note on triboluminescence, may I point out 

 that the study of the subject from a physical standpoint should 

 be extremely fertile. Saccharin may now, thanks to commer- 

 cial enterprise, be obtained in large quantities at a comparatively 

 low cost. William Jackson Pope. 



EXPLOSIONS CAUSED BY COMMONLY 

 OCCURRING SUBSTANCES. 

 'T'HE occurrence of a serious explosion in the Capitol at 

 Washington, last November, has led the President of the 

 American Society, Prof. C. E. Munroe, to address the members 

 on the subject of explosions caused by commonly occurring 

 substances. The address, which is fully reported in a recent 

 number of Science, forms an interesting and valuable history of 

 the subject, beginning with the well-known flour mills explosion 

 in Olasgowin 1872. A similar explosion in Minneapolis, in 

 1878, shattered walls six feet thick at the base, and projected 

 sheets of corrugated iron to a distance of more than two miles. 

 The origin of the explosion was traced to the striking of fire by 

 a pair of mill-stones through the stopping of the " feed. " Dust 

 explosions have also been recorded in connection with oatmeal, 

 starch, rice, malt, spice, saw-dust, soap and zinc. In pharmacy 

 and the arts accidents have arisen from various mixtures of 

 combustible substances and oxidising agents in connection with 

 matches, chlorate of potash lozenges, sodium peroxide and sodium 

 bisulphite mixtures. Among substances explosive /c?- sc which 

 have given rise to accidents, are erythryl nitrate, ammonium 

 nitrate, and various nitroso compounds, diazo bodies, diamides, 

 hydrazoic acid and its compounds, hydroxylamines, chlorates, 

 carbonyl compounds, permanganates, peroxides, chlorides and 

 iodides. Prof. Munroe devotes a considerable amount of space 

 to explosions arising from the use and storage of petroleum, 

 drawing his information mainly from English sources. He adds 

 to the examples, well known in connection with British ship- 

 ping, of explosions caused by the use of "driers" and paints 

 made up with volatile hydrocarbons. A remarkable explosion 

 occurred at Rochester, New York, in 18S7, owing to the leakage 

 of twelve thousand gallons of naphtha from a dislocated iron 

 main into a sewer. The explosive mixture of air and vapour 

 was ignited from a boiler fire through an untrapped water- 

 clo.set, and the explosion, besides causing loss of life, destroyed 

 three large mills. Prof Munroe states that of substances sup- 

 posed to impart safety to kerosene, alum and sal-ammoniac are 

 practically insoluble in the liquid, and are of no effect ; whilst 

 camphor, though it raises the flash-point, causes the vapour 

 mixed with air to have a lower temperature of ignition. 



After dealing with compressed gases and coal-dust explo- 

 sions. Prof Munroe reverts to the Washington explosion, and 

 shows that it was due primarily to the escape of gas through 

 a governor into a "live" 4-inch main, owing to a sudden 

 doubling of pressure. The gas found its way through a 

 labyrinth of passages and compartments in a section of the 

 building, and when the stratum of gas reached down to the 

 level of some burning gas jets, ignition took place and the 

 explosion was propagated in all directions, its intensity and 

 range being increased by the disturbance of large accumulations 

 of inflammable dust. 



NO. 1539, VOL. 59] 



TECHNICAL EDUCATION IN GERMANY} 

 C'^ ERMAN merchants and manufacturers are alive to the 

 ^^ importance of increasing the efficiency of the mechanics 

 and artisans, and of improving the quality of their gocds. 

 According to the United States Consul at Hanover, they 

 appear to be resolved that " Made in Germany " shall no longer 

 pass as a term of opprobrium, but be a synonym of excellent 

 materials and good workmanship. A meeting took place 

 recently in Hanover, which is likely to exercise a very 

 important influence in this direction. It was in the nature of a 

 conference, under Governmental sanction and direction, to 

 discuss German trade and manufacturing interests, and to devise 

 plans for their extension and improvement. It was held at the 

 instance of the Prussian Minister of Trade and Commerce, and 

 was presided over by the Oberregierungs President of the 

 Province of Hanover, Count Stolberg Representatives of the 

 Government from Berlin, the highest officials of the Hanoverian 

 provincial and municipal administrations, leading manufacturers 

 and business men, delegates from the Chamber of Commerce, 

 the manual training and artistic trade schools, and from the 

 working men's trade unions, attended and took part in the 

 deliberations. As a result of the conference, it was unanimously 

 resolved: (i) To establish at once in the city of Hanover 

 advanced lecture courses, in which artisans and apprentices in 

 all trades shall have an opportunity to complete their 

 mechanical education, and be instructed by experts how to 

 install and manage a model workshop, and work and use 

 machines and tools to the greatest advantage. Instruction will 

 also be given in book-keeping, the making and rendering 0, 

 accounts, the making of estimates of the cost of work and 

 materials, how to conduct business correspondence, drawing, 

 and other practical branches. (2) The supervision and control 

 of the said lecture courses shall be under the direction of a 

 commission composed of representatives from the Imperial, 

 provincial, and municipal administrations, the Chamber of 

 Commerce, the manual and art schools, and from the trade 

 unions. (3) The first course of lectures will be for cabinet- 

 makers, locksmiths, shoemakers and tailors. Those for other 

 trades will follow. (4) A fee for tuition will be exacted from 

 mechanics able to pay, but those unable to pay will be instructed 

 free. Funds for the payment of the tuition of the poor will be 

 provided by the Hanover provincial and municipal Govern- 

 ments. (5) Only mechanics and apprentices will be admitted 

 to the classes whose theoretical and practical knowledge is such 

 as to give promise of success as students. The Commission 

 has power in all cases to decide as to qualification of applicants 

 for admission. (5) Teachers are to be selected by the Com- 

 mission, and confirmed by the Minister of Trade and Commerce. 

 (7) The cost of the establishment and maintenance of the lectures 

 is to be supplied by the General Government, and that of the 

 province and city of Hanover, together with the trades unions, 

 the Chamber of Commerce, and others interested therein. (8) 

 It is further intended that great care shall be used in teaching 

 apprentices how to obtain the most practical advantages from 

 the knowledge obtained by them in the classes. To this end, 

 the creation of working-men's co-operative societies is to be 

 urged. (9) A permanent exhibition of all power machines and 

 tools used in the small trades is to be established in the Gewerte 

 Halle (Industrial Hall) in Hanover. The machines exhibited 

 there are to be worked by competent mechanics, who, on 

 request, will exhibit their uses and management to all inquirers. 

 In connection with the machine exhibition, there will also be 

 established an exhibition of sample products, in process of 

 manufacture, as well as finished. (10) In order to enable small 

 manufacturers and tradesmen to purchase their raw materials at 

 wholesale prices, and to facilitate the sale of their products, the 

 formation of co-operative stores is to be encouraged. Consul 

 Anderson has been informed that the establishment of these 

 courses of lectures to mechanics is the initial move in a general 

 plan to be in all the main labour centres of Germany, dependent 

 upon the success of this experiment. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 Oxford —The following are the chief lectures advertised 

 for the ensuing term in the 'Faculty of Natural Science, in addi- 

 tion to the elementary courses :— Prof. Gotch, on the nervous 

 system; Dr. Mann, on histology of sense organs ; Mr. Burch, 

 1 Reprinted from the/^iown/ of ihe Society of Art5 (.April 14). 



