indistinct in outline when seen by ordinary light, but become well defined when examined with a half-inch objective between crossed prisms.

Two analyses of this rock afforded Mr. J. A. Phillips the following results:

Anyone who has made a careful examination of the Tertiary phonolites, or is acquainted with Professor Zirkel's researches on them, will at once recognize the identity of their mineralogical composition with the rock here described, and will be struck with the thoroughly characteristic appearance of the nepheline, which is absolutely the same in both. In fact, no one would hesitate to call it a phonolite, if it were known to be of Tertiary age. The age, however, is unknown, and likely to remain so, for the rock stands alone in the sea, and its actual relations with others cannot be observed. Situated between the Land's End and Scilly Islands, it is in a Palæozoic district, disturbed and penetrated in all directions by granites, porphyrites, and diorites; few, therefore, will hesitate to place it among the older series of igneous rocks. It is at present the practice among many petrologists to name rocks according to their supposed geological age; a dark-coloured augitic rock, for example, would be a basalt if of Tertiary age, but must be a melaphyr or aphanite, if of some indefinite early age. In accordance with this absurd system, the rock in question would probably be called a Foyaite, if it were known to be old, as it agrees well with descriptions of that rock, except that the elæolite is here represented by nepheline crystals which cannot be distinguished from those of true phonolites.

After some hesitation, I have adopted the name of porphyritic phonolite for this rock, and will take the present opportunity of suggesting that one name only should be assigned to all igneous rocks composed of the same constituent minerals, irrespectively of their age; or, in other words, that we should assimilate the nomenclature

*Of which 94 was lost in water-bath.

to that employed in the sedimentary rocks. We speak of Carboniferous or Tertiary sandstones, &c., why not Carboniferous or Tertiary dolerites or melaphyres? When the age cannot be precisely ascertained, an approximation may generally be made, and such terms as post-Carboniferous, ante-Triassic, &c., might be used.

If some such system were adopted, all the basic, augitic rocks containing much iron oxide, would form one group, and we should get rid of a number of useless names which have been applied to rocks in utter ignorance of their mineralogical composition or

structure.

Until quite recently such a suggestion could not have been adopted, as there were no means of ascertaining with certainty the constituents of the fine-grained rocks; but now that improved methods of microscopical research are available, it is quite time that the unscientific nomenclature still in use should be supplanted by one more in accordance with the present state of knowledge.— Geological Magazine, June.

VIII.-On Spore-cases in Coals.

By J. W. DAWSON, LL.D., F.R.S.

WHEN in London, last year, Prof. Huxley was kind enough to show me some remarkably beautiful slices of coal mounted by his assistant, Mr. Newton, and showing with great distinctness multitudes of spore-cases and spores, some of them very well preserved. He further stated to me his belief that such material had been largely or mainly instrumental in the production of Coal. At the time I declined to accept this conclusion, on the ground that the specimens probably represented layers of coal exceptionally rich in spore-cases; and that even in these specimens a large quantity of matter was present which long experience in the examination of coals enabled me to recognize as cortical or epidermal matter, which I had previously shown by my examination of the coals of Nova Scotia to be the principal ingredient in ordinary coal. I promised, however, on my return to Canada, to look over my series of preparations of coal, with a view to the occurrence of spore-cases, and also to make trial of the somewhat improved method of preparation employed by Mr. Newton. On my return I gave the results of my examination to Prof. Huxley, in a letter which he has quoted in the brilliant exposition of his observations and conclusions in the 'Contemporary Review' for November, and which will probably give a tone to the representations of popular writers on this subject for

* In the quotation the word “cubical” has been substituted for "cortical."

some time. While, however, admitting the great interest and importance of Prof. Huxley's observations, and prepared to contribute some additional illustrations of the occurrence of spore-cases in coal, I think it well to direct attention anew to the actual composition of the substance, as proved by its mode of occurrence, and illustrated by my own extensive series of observations on the coals of Nova Scotia and Cape Breton, including the series of eighty-one seams exposed at the South Joggins, the whole of which I have examined in situ and under the microscope.

The occurrence of bodies supposed to be spore-cases in coal, is, as Prof. Huxley states, no new discovery; but in reality these may be said to be the first organisms recognized by any microscopic observer of coal-that is, if all the clear spots and annular bodies seen in slices of coal are really spore-cases. They were noticed by Morris as early as 1836, and they had been observed and described long before by Fleming in Scotland. Goeppert mentioned and figured them in his "Treatise on Coal' in 1848. Balfour described them in 1859 as occurring in Scottish coals, and Quekett figured them in his account of the Torbane Hill mineral in the same year. In 1855 the latter microscopist showed me in London slices exhibiting round bodies of this kind, very similar to those now described by Huxley; but at that time I regarded them as concretionary, though Prof. Quekett was disposed to consider them organic. Mr. Carruthers has summed up most of these facts in his account of his genus Flemingites in the Geological Magazine' for October, 1865. The subject has also attracted the attention of microscopists in connection with the Tasmanite, or "white coal" of Tasmania, which is composed in great part of the spore-cases of ferns.

I suppose that the oldest spore-cases known are those described by Hooker, from the Ludlow formation of the Upper Silurian; but these, if really spore-cases, are different in structure from those ordinarily found in the coal formation, more especially in the great thickness of their walls, and I am not aware that they have anywhere been found in considerable quantities.

The oldest bed of spore-cases known to me, is that at Kettle Point, Lake Huron. It is a bed of brown bituminous shale, burning with much flame, and under a lens is seen to be studded with flattened disk-like bodies scarcely more than a hundredth of an inch in diameter, which under the microscope are found to be spore-cases, slightly papillate externally, and with a point of attachment on one side and a slit more or less elongated and gaping on the other. I have proposed for these bodies the name Sporangites Huronensis. When slices of the rock are made, its substance is seen to be filled with these bodies, which, viewed as transparent objects, appear yellow like amber, and show little structure, except that the walls can, in some cases, be distinguished from the internal cavity, and the

VOL. VI.

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latter may be seen to enclose patches of flocculent or granular matter. In the shale containing them there are also vast numbers of rounded translucent granules which may be the escaped spores.

The bed at Kettle Point is stated in the report of the Geological Survey to be 12 to 14 feet in thickness; but to what degree either in its thickness or horizontal extent it retains the characters above described, I do not know. It belongs to the Upper Devonian, being supposed to be a representative of the Genesee slates of New York. It contains stems of Calamites inornatus and of a Lepidodendron, obscurely preserved, but apparently of the type of L. Veltheimianum, and possibly the same with L. primævum of Rogers. The sporecases are not improbably those of this plant, or of the species L. Gaspianum, which belongs to the same horizon, though not found at this locality. The occurrence of this bed is a remarkable evidence of the abundance of Lycopodiaceous trees, whose spores must have drifted in immense quantities in the winds, to form such a bed. It is to be observed, however, that this is not a bed of coal, but a bituminous shale of brown colour, and with pale streak, no doubt accumulated in water, and even marine, since it contains Spirophyton* and shells of Lingula. In this it agrees with the Australian Tasmanite, which, though composed in great part of spore-cases of ferns, is, as I am informed by Mr. Selwyn, an aqueous deposit, containing marine shells.

There is, however, one bed of true coal known in the Devonian of Eastern America, that of Tar Point, Gaspé, and it is curious to observe that this is not composed of spore-cases, but of successive thin layers of rhizomata and stems of Psilophyton, with occasional fragments of Lepidodendron and Cyclostigma. Rounded disks, which may be spore-cases, occur in it, but very rarely. In the bituminous shales associated with this coal the microscope shows amber-coloured flakes of irregular form, but these are easily ascertained to be portions of the epidermis of Psilophyton, or of the chitinous crusts of crustaceans which abound in these beds.

Ascending to the Lower Carboniferous (sub-carboniferous), there are great quantities of rounded spore-cases of the size of mustard seeds (Sporangites glabra of my papers) in the rocks of Horton Bluff and Lower Horton, Nova Scotia. They are sometimes globular, and filled with pyrite of a granular texture which perhaps represents the original cellular structure or the microspores. În other cases they are flattened and constitute thin carbonaceous layers. They are almost without doubt the spore-cases of Lepidodendron corrugatum, which abounds in the same beds, and constitutes in one place a forest of erect stumps. I described them in a paper "On the Lower Carboniferous of Nova Scotia," in the Proceedings of the Geological Society of London' for 1858, though not then aware of

* The well-known Cauda-galli fucoid.

their true nature, which was, however, recognized by Dr. Hooker in some specimens which I had sent to London.

In my paper "On the Conditions of Accumulation of Coal,"* I proposed the name Sporangites for these bodies, in consequence of the difficulty of referring them certainly to any generic forms. Carruthers had, in Oct. 1865, described a cone containing rounded sporecases of not dissimilar type, under the name Flemingites. In the paper above referred to, I stated that out of eighty-one coals of the South Joggins Section examined by me, I recognized these bodies and other fruits or sporangia in only sixteen; and of these only four had the rounded Lycopodiaceous spore-cases similar to those of Flemingites. These are the following:

(1.) Coal group 12, of Division IV., has a bed of coal one foot thick, of which some layers are almost wholly composed of Sporangites papillata.

(2.) Coal group 13, Div. IV., has in some layers great quantities of Sporangites glabra, especially in the shaly part of the coal. (3.) In Coal group 14, Div. IV., a shaly parting contains great numbers of similar sporangites.

(4.) In Coal group 15a, Div. IV., the shaly roof abounds in sporangites, but I did not observe them in the coal itself.

In addition to these cases, all of which curiously enough occur in one part of the section, and among the smaller coals, I have noted the occurrence of clear amber spots in several of the compact coals, but I did not regard these as certainly organic, suspecting them to be rather concretionary or segregative structures.

The great coal beds of Pictou are, in so far as my observation. has extended, remarkably free from indications of spore-cases, and consist principally of cortical and ligneous tissues with layers of finely comminuted vegetable matter. A layer of cannel, however, from a bed near New Glasgow has numerous flattened amber-coloured disks, which may be of this character. In those of Cape Breton, the yellow spore-case-like spots are much more abundant; but these coals I have less extensively examined than those of the mainland of Nova Scotia. Of American coals, the richest in spore-cases, that I have seen, is a specimen from Ohio, which contains many large spore-cases, and vast numbers of more minute globular bodies apparently macrospores. It quite equals in this respect some of the English coals referred to by Huxley. I have also a specimen of anthracite from Pennsylvania, full of spore-cases, some of them retaining their round form and filled with granular matter which may_represent the spores.

It is not improbable that sporangites or bodies resembling them, may be found in most coals; but the facts above stated indicate that their occurrence is accidental, rather than essential to coal accu

* 6 'Proceedings of Geological Society of London,' May, 1866.