. The Canadian record of science. Natural history. The Monteregian Hills. 243 shown in Fig. 7. The opening occupied by the intrusion was in all probability formed by the perforation of the horizontal shales at this point by the explosive action of the steam and vapors preceding the eruption proper, as it presents exactly the features reproduced by Daubr^e in his highly suggestive experiments on the penetrating action of exploding gases. It is, in fact, what he terms a diatreme. Des perforations aussi remarkables, tant par leurs formes que par les communications qu'elles ont etablies avec les p
. The Canadian record of science. Natural history. The Monteregian Hills. 243 shown in Fig. 7. The opening occupied by the intrusion was in all probability formed by the perforation of the horizontal shales at this point by the explosive action of the steam and vapors preceding the eruption proper, as it presents exactly the features reproduced by Daubr^e in his highly suggestive experiments on the penetrating action of exploding gases. It is, in fact, what he terms a diatreme. Des perforations aussi remarkables, tant par leurs formes que par les communications qu'elles ont etablies avec les profondeurs du sol, con- stituent, parmi les cassures terrestres, un type assez nettement characterise pour meriter d'etre distingue par une denomination pre- cise et cosmopolite. Le nom de diatreme rapelle l'origine probable de ces trouees naturelles, veritables tunnels verticavx, qui se rattachent souvent, comme mi incident particulier, aux cassures lineaires, dia- clases et Fig. 7-—Diagrammatic cross-section of Mount Johnson, showing the relation of the several rock types. The occurrence is one which presents a close re- semblance to the remarkable volcanic necks recently described by Sir Archibald Geikie2 in East Fife, and also to those described by Branco,3 in Wtirtemberg. Mount Johnson, however, is a neck occurring in an area which has undergone much more extensive denudation since the time of the intrusion than in the cases above mentioned, and as a consequence of this the fragmental material 1 "Recherches experimentales sur le role possible des gaz a hautes temperatures doues de tres fortes pressions, etc!," Bull, de laSoc. Gdol. de France, 3e serie, tome XIX (1891), p. 328. 2 The Volcanic Necks of East Fife. Glasgow : Hedderwich & Sons. 3 Schwabens 125 Vtdcan-Embryonen und deren tufferfiillte Ausbrurhs- rohren das grosste Gebiet ehemaliger Maare avf der Erde. Tubingen, Please note that these images are extracted from scanned page ima
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