April 4, 1913. THE COLLIERY GUARDIAN. 697 owing to the fluffy nature of the substance; in other cases the sample received contained no such fine dust. The ignition-temperatures in such cases have no relative value, and the experiments made serve only to show whether or not the substance is dangerously inflammable. Dr. Wheeler observes that under the conditions obtaining in the test the formation of the ignitible mixture of gas and air will depend upon (1) the tempera- ture of the source of heat; (2) the amount of dust heated up in any small column of the cloud which traverses the coil in unit time, and therefore upon the density of the dust cloud; and (3) upon the readiness with which inflammable gas is evolved from the dust. Given, there- fore, that the second factor can be kept constant for different dusts, differences in the temperatures of ignition observed afford a measure of the relative ease with which a particular dust evolves inflammable gas, and, therefore, of its sensitiveness to inflammation. It will be under- stood, however, that when dealing with dusts of widely different physical character it is by no means easy to ensure that the density of the dust cloud passing over the source of heat is constant; and the same reliance cannot, therefore, be placed upon the relative tempera- tures recorded as in the case of different coaldusts. In Test No. 2 attempts were made to determine the lowest temperatures at which ignition can be effected in the case of all the dusts already subjected to Test No. 1. According to the test sugar and dextrine once more appear as the most readily inflammable of all, the temperature at which ignition could be effected being 540 degs. Cent.—i.e., well below red heat. Most of the remaining dusts have practically the same ignition temperature (600 degs. to 650 degs. Cent.). The most noticeable exceptions amongst those dusts that are capable of propagating flame are copal gum (750 degs.), “ dead ” cork (740 degs.), gramophone record dust (750 degs.) and leather (740 degs.). Other dusts classed as inflammable (Classes I. and II.) that have ignition temperatures higher than the normal are shellac compo- sition, cork (in the case of one sample), chicory, horn meal and mustard. These divergences from the normal are probably caused by the evolution of uninflammable gases in greater quantity than occurs with most inflam- mable dusts ; or by the presence of much incombustible dust. The sample of shellac composition obviously owed its high ignition temperature (780 degs.) to the presence of much incombustible dust. Since a reduction in the percentage of incombustible dust would render it more inflammable it is placed in Class II., despite the fact that Test No. 1 showed that the particular sample tested was incapable of propagating flame. A sample of gramophone record dust also, containing 32 8 per cent, of incombustible dust, had a high ignition temperature according to test No. 2. Test No. 1, how- ever, showed that, once ignited, it was capable of propa- gating flame fairly readily. It is therefore placed in Class I., since a reduction in the quantity of incom- bustible matter present would render it more readily ignited. Copal gum, leather and “ dead ” cork present cases somewhat different to the above. They did not contain a high percentage of ash, and they propagated flame when subjected to Test No. 1. Their ignition temperatures according to Test No. 2 are, however, high. This can be accounted for by assuming that a consider- able quantity of incombustible gases are mixed with the combustible gases evolved on heating the dusts. Their high ignition temperatures would be due, according to this assumption, not to an adventitious circumstance such as is the presence of incombustible dust, but to an inherent quality. They are therefore placed in Class II. With these exceptions the dusts are grouped on the principle that Class II. contains those which, whilst incapable of propagating flame when submitted to the small source of heat and short duration of heating of Test No. 1, inflamed readily when submitted to Test No. 2, and are, therefore, presumably, capable of propa- gating flame when the means of ignition is compara- tively severe. Class I. contains all those dusts that propagated flame readily under Test No. 1. Manchester Geological and Mining Society.—A meeting of the Manchester Geological and Mining Society will be held at Queen's Chambers, 5, John Dalton-street, Man- chester, on Tuesday, April 8, 1913, at 4 p.m. The following paper will be read :—Small Coal and Dust, Production, Prevention, Treatment and Utilisation (with special reference to Dry Mines),” by Mr. John Drummend Paton. The paper will be illustrated by a series of lantern slides The following papers will be open for disccussion:— “ Colliery Cables,” by Mr. W. T. Anderson; “ The Relation between Subsidence and Packing, &c.,” by Mr. George Knox; and “ The Hydraulic Stowing of Goaves,” by Mr. George Knox. THE WESTPHALIAN EXPERIMENTAL STATION AT DERNE * Bergassessor Beyling and Bergassessor Zix. The lack of a sufficient supply of firedamp for carry- ing on the various tests, and the proximity of inhabited houses, necessited the removal of the old experimental station of the Westfalische Berggewerkschaftskasse at the Consolidation Colliery, near Gelsenkirchen, to a new site, the selection of which was influenced by the con- sideration that the Knappschafts-Berufsgenossenschaft projected the construction of a large experimental gallery for investigating the causes of firedamp and coal- dust explosions. The amalgamation of the two projects having been decided upon, a site in a sufficiently remote position was found in the community of Kirchderne, nearly 5 miles north-east from Dortmund, and about 1,100 yards south-east from the Gneisenau Colliery, which is able to furnish a supply of pure firedamp in abundant volume. The site is triangular, and covers an area of about 10 acres, enclosed in a strong boarded fence 8 feet high* As can be seen from the plan (fig. 1) the installation SHEDS 9 9 0 Q ! Q Q. Q Q Q Q Q Q Q 0 f Q Q Q a 9 o Q a ’ Q. Q Q Q Q Q 9 o 9 Q q Q Q 0 Q Q Q 0. Q: Q Q ® ° o ’ 9 0 9 9 q 9 • Q n 9 P 9' „ Q— 0’9 0 O Q Q Q 0 jQ 0 0 9 Q ‘ Q > V 9 9 Q o 9 Q