166 PKOF. T. R. JONES — IMPORTAKCE OF 



As to the Diatoms, they are found in very many localities ; but 

 the enormous masses which accumulate from their growth in some 

 places is something astonishing. This diagram (exhibited) shows 

 some Bacillarice among Confervae, etc. They are tiny siliceous 

 atoms finer than wheat flour. But their number is not more 

 astonishing than their elegant shapes. In some parts of the sea, 

 as in the Antarctic Ocean, deep soundings long ago proved that the 

 sea-floor is covered with beds of Diatomacese. Fossil deposits of 

 these minute organisms are worked for use as polishing-powder and 

 for other purposes. Richmond and Petersburgh, in Yirginia, 

 stand on diatomaceous marls, 20 feet thick. In Bohemia, at Bilin 

 the "polishing-slate," and at Pranzenbad the "flint-fi'oth," are well 

 known. So also the polishing-powder got near Tripoli and so 

 named, also the "Mountain-meal" of Sweden, and similar siliceous 

 earths in the Isle of Mull, — near Dolgelly, — and on the banks of 

 the river Bann and elsewhere near the Mourne mountains in the 

 county Down, are all composed of these microphytes. That from 

 the Bann has been sold as "Lord Koden's plate-powder." Being 

 composed of little sharp fragments, it can take off the surface of 

 metals, and polish them by giving them a new face. Such a 

 material is also found in the " Dutch rush " or E(iuisetum, which 

 has so much of silica in it, that, when dry, it can be used as 

 rubbing material to polish iron and other metals. In the bamboo 

 and other canes silica is also found, and grasses and wheat would 

 not stand upright if it were not for the siliceous atoms. You know 

 that when hay or '^orr is burnt accidentally, of the rick there will 

 only rerauiri a h" ,: : . oi slag, rough, scoriaceous, and glassy, due to 

 the' presence of my^ii^is and myriads of these tiny atoms. So you 

 see these minute aton}> are very important in life for some of these 

 plants, and often pla;: m important part after death. 

 • There is another l.^rm of vegetable matter occurring in very 

 minute atoms, which is, perhaps, of still more importance. A 

 puff-ball when dry .nd broken emits a cloud of delicate dust. 

 Among thr many fine specimens of Pungi on the table, some will 

 supply what we wish to see. The atoms constituting these impal- 

 pable smoky elouds — i}idefinitely small to our naked eyes, and not 

 recognizable without a microscope — are really analogous to one of 

 the most important accumulations without which we cannot get 

 on in every-day life. You know also that the Lycopodium in its 

 fiLiiitisc gives off simiiar clouds of dust, or "spores," which come 

 from little vesicles or spore-cases arranged differently from the 

 spores of ferus, being packed in cones, in a most symmetrical and 

 masterly uicinuci. TLjre are fossil remains of ckib-mosses which 

 have given off such clouds of this fine spore-dust and produced 

 such masses of the little vesicles in which the dust has been 

 stored up and arranged, in past times, that we actually owe a great 

 deal of our coal, and some of the best of it, to the organic dust you 

 see there (Diagram referred to). The club-mosses now in the 

 rocks were large trees, but nevertheless they were club-mosses, like 

 lycopodiums and selaginellas, but of the kinds known as Lepido- 



