Notes and correspondence

Composition of the Boghead Coal — In compliance with the request of the President of the Microscopical Society, I beg to send you a copy of the results of my examination of the Boghead mineral, called Boghead coal (brown variety).

It is of a dingy drab colour, very compact and difficult to pulverize ; it has a slaty somewhat conchoidal fracture, and is easily scratched by the nail, a light-brown streak being left. Burnt in a crucible it evolves an abundance of exceedingly luminous gas, and the (coke ?) left retains exactly the form of the mass submitted to distillation, and is of whitish colour. This so-called coke will not burn, but when ignited in contact with the air it leaves a white ash. Reduced to very fine powder, and treated with coal-naphtha (the same as is used in the manufacture of marine glue), the mineral yields a brown solution, which evaporated leaves a resinoid mass, and the residue left after treatment with the above-mentioned menstruum may be partially dissolved by treatment with boiling concentrated sulphuric acid.

The specific gravity of the samples examined varies from 1173 to 1-179.

Its constituents are as follows : —

Composition of the ashes:—

A. Normandy, 67, Judd Street, Brunswick Square.

The Boghead Coal. — I have just received the Journal, and I find in it a statement, copied from the ‘Commonwealth,’ which I must correct. It is there stated, that I said at the Royal Society of Edinburgh that I regarded the Torhane mineral as differing from bituminous shale, because I could not extract bitumen from it by any solvent.

Now what I really stated was this, “that bituminous coal and bituminous shale were wrong names, inasmuch as no true bitumen existed in either, or could be extracted by those solvents in which true bitumen is soluble. I added that the combustible matter in the mineral was, like that of coal, not true bitumen, and that I could find no chemical difference between it and the combustible part of ordinary coal. Some persons regarded the mineral as earthy matter which had become impregnated with bitumen,; but this was not the case, if by bitumen be meant the substance, allied to asphalt, commonly so called. My argument was that since I could find no chemical distinction between the combustible matter in this mineral and that in coal, the mineral was, chemically considered, a coal. As to structure, that is often wanting in portions of coal, and besides, Dr. Traill had just said that no true distinction could be founded on the absence of structure.”

By the report in the Journal I am made not only to say nearly the reverse of what I did say, since I maintained the identity of the combustible or bituminous matter in coals, shales, and the mineral, but I am made to talk downright nonsense, as if I maintained that solvents could extract bitumen from shale, which I said they could not.

Allow me also to point out that the Reviewer of Fresenius on Mycology has made a mistake in translating Unscheinbarkeit “unsightliness.” It means not precisely invisibility, but the want of obvious perceptibility ; and F. means to say that it is so difficult to see the structure and organs of fungi that people are thereby deterred from the study. The phenomena are too obscure, too little apparent, to attract the many. This is his true meanings for which no single English word will suffice. — WILLIAM GREGORY, Edinburgh.

A defence of the proposed new genus “Actinophœnia” — Shndbolt. — IN a paper by Mr. Roper on the “Diatomaceæ of the Thames,” read before the Microscopical Society in January of the present year, that gentleman alludes to a species previously described by me (under the name of Aetinophœnia splendens, occurring in the Port Natal gathering of Diatomaceæ, and also found abundantly in the Guano from Callao), as being probably somewhat similar to one found by him amongst the Thames deposit, but he refers his species to the genus Actinocyclus of Ehrenberg, under the specific name sedenarius. As it is evident from the remarks which accompany his description that he has mistaken my reasons for not classing the species in question as he has done, it is probable that others may have not comprehended them ; and I think it right, consequently, to endeavour to show, that my object was not a needless multiplication of genera, more especially as I perceive from Mr. Roper’s drawing that our attention is directed to one identical plant.

I am aware that it may look like presumption in me to enter the lists against so great an authority as the learned Professor quoted ; but, in the first place, I am by no means satisfied that I really do differ from Ehrenberg, and even if I do, it is by no means surprising that a minute flaw should be perceptible to the Lilliputian that was overlooked by the giant.

In all the Actinocycli proper, the number of segments formed by the septa is always even, and every alternate segment occupies a position in a different plane from that in immediate contiguity to itself. This is so marked a character, that it cannot fail to be observed when once pointed out. The front view presents an undulating outline, and the two valves are so placed that the alternate segments in each fit into one another, the septa also coinciding; but in the genus which I have called “Actinophœnia,,’ the case is in every way different even according to Mr. Roper’s own description (the correctness of which I quite admit), for here, as in the genus “Arachnoidiscus” the segments are all in one plane, and the septa all in another, being placed internally. Moreover, the front view of the two valves presents a sort of double scallop in outline ; and to crown the whole, the septa of the inferior valve are not placed opposite to those in the superior one, but intermediately. Surely all these points are sufficient to establish a generic difference ; but if not, there is another to which I would direct the attention of microscopists, viz., the structure of the frustule. In the genera Actinocyclus, Coscinodiscus, Triceratium, Acti- nophœnia, and Arachnoidiscus, I have most distinctly and unmistakably detected the presence externally of a sort of membrane not unlike cellulose, having very minute reticulations, puncta, or cells (according to the fancy of the observer) ; for they are so minute that it is impossible to pronounce with any degree of certainty even when viewed under the very highest powers of our finest instruments ; and this external membrane is not brittle like the siliceous part, but tough and capable of being folded and unfolded without its necessarily breaking ; and this in the genus “Arachnoidiscus” I have actually accomplished, and recorded the fact in a paper published in the ‘Microscopical Society’s Transactions.’ This external membrane is in all the genera I have quoted, supported by a siliceous framework ; but if we examine those of Actinocycli and Actino- phœnia, how different they appear, the one having a strong siliceous network between the septa, and the other being quite destitute of such an appendage. It seems that Mr. Roper has noticed the membrane to which I have alluded, but has not probably been aware of its character ; and has evidently fallen into the error of supposing that I had relied upon that as a characteristic difference, because the markings are exceedingly patent in Actinophœnia from the absence of the net-like reticulations in the siliceous part, and somewhat obscured by their presence in the Actinocycli, and the other genera previously mentioned.

One other objection I have to make is to the specific designation sedenarius, founded upon one of the most inconstant characters that can be employed, viz., number — and it unfortunately happens in the present case, that the variation in the number of septa is so frequent, that seventeen to twenty might quite as well have been selected as the number employed. I am aware that Mr. Roper merely took up what he conceived to be Ehrenberg’s view, and that the specific designation was not of his selecting ; but if he will examine a slide of Callao Guano, he will, I am sure, be satisfied as to the inconstancy in the number of septa.

Under all these circumstances, I submit that I have adduced sufficient evidence to establish the claim of the “Actinophœnia?’ to a separate generic distinction, whether I have chosen a proper designation or not, I must leave to others to decide. — George Siiadbolt.

On a Developing Solution for Microp holographs made by artificial Light.—The developing solution, of which the formula is here given, appears to possess a considerable advantage over pyrogallic acid, used in the common way, in the production of microphotographic collodion negatives. The black is much more intense than that which I have been able to procure by the use of pyrogallic acid, and the lights fully as clear, if not more so. That it will keep, is also an advantage, though a trifling one, as it can be made extemporaneously in a few moments at any time. Whether it will answer as well for microphotographs made by daylight, and for the usual camera-pictures, my experience will not allow me to state ; for the latter I have fancied it not well adapted — but why, I do not know. The solution is made by dissolving in 1 fluid ounce of water, acidulated with two drops of nitric acid. It is, perhaps, needless to remark that the iron-solution without the tartaric acid, answers very well for positives on the glass. The light I have used for microphotography has latterly been common gas, with a good Argand burner, which I find quite sufficient for the 4-10ths and under. The time required is from 5 minutes to 15 minutes. Under longer exposure the collodion begins to dry.—G. B.

Mode of Growth of Parasitic Fungi.—As all the scientific men of this country agree in opinion as to the mode of attack and growth of fungoid diseases on plants, it may seem presumptuous, if not superfluous, to add anything to what has already been said upon the subject. May it not, however, be possible that many of these men whose names stand so high as to cause their opinion to be received as authority, without further investigation—may it not be possible that in the great variety and multiplicity of their pursuits they may have passed over so comparatively unimportant a subject ? For, if they had brought the full powers of their investigations to bear upon it, they could not fail to have been convinced of what I am now about to advance : that fungi do not enter and ramify in the tissues and send up stems through the stomata of living healthy plants,^* but that they only grow upon the surface, as may easily be seen, if proper care be observed in preparing sections for the microscope. I have bestowed a great deal of time and attention on the subject, and feel fully convinced that the mode of growth of this class of fungi is as represented in the annexed illustration, which, should you think it, with the accompanying remarks, worthy your notice, you will oblige by inserting in your excellent Journal for April. — EDWARD TUCKER, Margate.