THE CHEMICAL NEWS, VOL. CXXV., No. 3264 MINERALS DEPOSITED BY BACTERIA IN MINE WATER. OBSERVATIONS IN THE KIMBERLEY DIAMOND MINES. (Continued from Page 243.) After Mr. Drew's results, there appears now nothing anomalous in inferring the assistance of bacteria in producing such deposits as ours, and I am tempted to infer that it is the persistent activity of such organisms-be their origin what it mayover this long period of time that has been largely operative in producing them. I do not claim that we have secured the actual Bacillus Calcis of Mr. Drew, but we do at any rate appear to have met with n organism possessing somewhat similar functions. Further interesting features were observed, when some of the pipe deposit was finely powdered and examined under the microscope. Innumerable parallel striations were visible on nearly every partici; the spaces between them measuring from 1/600 to 1/2,000 of an inch (Fig. 4). By carefully adjusting the focus, the fractured ends of many of these particles presented a series of little steps, revealing their structure as composed of extremely thin layers of these thin layers was quite homogeneous superimposed one upon another, and each and almost transparent. A thin portion of the deposit from one of the stones was cut off at right angles to the surface, and ground down to a tenuity suitable for microscopical inspection. (Fig. 5). Owing to the brittle nature of the material, the preparation of this slide was a very tedious operation, and required the most delicate and patient handling. Even now the photo is not so good as one could wish, and only a tiny portion of the mounted specimen was sufficiently thin to allow a photograph being taken through the microscope (Fig. 6). This affords some idea of the very great number of layers that has gone to build up this mass. The only feasible explanation that I can offer for the deposition of these extremely fine layers one upon the other, is that it is the work of these same micro-organisms. When first observed in our bottle of water, they had produced on the glass an extensive transparent adhesive film of matter. This water was collected as it dripped from the roof. The stones were coated by the same process of dripping. Each drop fa:1ing on the more or less flat surface of a stone tends to flow all over it, thus at the same time evenly distributing its micro inhabitants. As a result of the intense activity of such myriads of organisms, it is not long before a strongly adherent, thin confluent film of calcareous matter is produced. By the time another drop falls on the same spot, a bed or layer of the earlier drop is established, and the second drop then proceeds to repeat the process, and thus layers are produced continuously, though slowly, one upon another, with every succeeding drop that falls on the stone. It is to be noted, in view of the rather considerable area of the roof over which the water trickles, that the fall of drops seems fairly rapid; but the dropping is very uneven, so that a drop seldom fal's from the same place except at long intervals. It is not surprising, therefore, thit a great deal of time is required to produce even of an inch of these deposits on any one article. as There are, of course, alternative natural processes which suggest themselves probable causes of such deposits. Stalactitic formations sometimes show very thin concentric layers; but these are in doubtedly produced by a process of evaporation and from fairly strong solutions of Bicarbonate of Lime; but such evaporation seems to be ruled out in the case of our samples. Moreover, none of these deposits ever assume stalactitic form. Travertine, too, and other native forms of Calcium Carbonate, are assumed to form from the action of certain algae, which, by absorbing the semi-combined CO,, in the absence of free CO,, causes CaCO, to fall out of solution. This cause is not excluded here, though, so far, no evidence has turned up in support of it. Again, too, the algae do not absorb the Calcium Car bonate into their structure, while the organisms found on the sides of our bottle can be easily shown to consist largely of the Calcium Carbonate. However, further bacteriological work is being carried out in connection with this matter. There is still another problem presented by these anomalous deposits which requires elucidation, viz., the colour of the mass and the brilliantly black surfaces. What is this colouring matter and whence derived? When fragments of the pipe core were shown to individuals curious enough to speculate as to their nature, they usually declared, without hesitation, that it was a specimen of crocidolite (cat's eye stone). After only a superficial microscopical inspection, this is not an entirely unreasonable suggestion, as the polished pieces of it do strikingly simulate that mineral. Its fibrous structure and colour are, however, the only features it possesses in common with crocidolite. Its brittleness and chemical composition sufficiently indicate that it cannot be this substance. native Another suggestion, offered by some wno were acquainted with its source, was that it was derived from the insulating material of old electric cables lying in the mine. This was quite feasible and operations were conducted to decide this point. The substances that would be removed from such material by a soda alkaline water (such as this water is) are resin and shellac. There are excellent chemical tests for identifying these two bodies, but after separating the organic matter from the calcium carbonate by a special method and submitting it to these particular tests, the answer, as a Cabinet Minister would say, was in the negative. The electric cable origin may therefore be eliminated from further consideration. A third suggestion was that it was the fossilised trunk of a tree. When a long piece of the pipe core is inspected, it does rather resemble a tree stem with the central portion removed. But of course fossiilsed trees do not grow in modern 6 inch iron pipes in diamond mines. After inspecting these various deposits in situ, two probable sources of this colouring matter seemed pretty obvious: it may have been derived from rotten timbes; or from soluble portions of animal excreta, or from both. Both occur in the mine, and in contact with a water containing so active an alkali as carbonate of soda, some of them would be carried into solution. The fact, that practically all these coloured deposits occur in the immediate vicinity of the shaft, where there is always much timber, and trickling alkaline water, at once suggested a ligneous origin for this colour. A great deal of work was performed to prove this point, though less would have sufficed had it not been for the other obvious alternative. The evidence for the influence of excrementitious matter slight and therefore inconclusive; the pre was sence of small quantities of ammoniacal compounds and traces of phosphate of lime being the only indications. Moreover, these were not present in all the samples that were operated on. Attention was therefore mainly devoted to confirming the woody origin. There are a great number of definite and indefinite chemical bodies existing in wood: some exceedingly complex; and to isolate and identify them all would occupy far more time than can be spared in a busy laboratory, and it would, besides, be quite unnecessary. Cellulose is a substance that is derived entirely from vegetable matter. It is a product of the so-called metabolism of living plant tissues, so that, if we meet with a substance in an alkaline water, which after isolation, responds to the generic tests for celluloses, we may reasonably conclude that that water has been in contact with woody matter in some stage of its travels; and if, further, we can isolate the same kind of substance from the actual deposit, which we know to be derived from the water, the inference is again perfectly logical that some, at any rate, of this organic matter has been acquired from the same source. Not to unduly enlarge this report, I may state as a result of many carefully con ducted experiments and tests, I was able to isolate from both the water and deposits, an organic substance which exhibited al' the characteristics of a cellulose material. This result was further confirmed in another way. Some of the decayed timber, which was brought from the mine, was digested with water containing carbonate of soda (N/20), thus imitating as far as we could the conditions we imagined to have occurred in the mine. When the organic matter derived from the timber by this means was isolated from the water and tested, precisely the same results obtained for cellulose material as in the original samples. were We may now, therefore, state unequivo cally that the unusual colour of all these deposits is derived from decaying timber after contact with an alkaline water. As a final proof that these alkaline waters do come in contact with timber, the slight muddy deposit that was obtained from one of the samples of alkaline water that was collected as it trickled down the walls of the shaft, was examined by means of the microscope. Every portion inspected revealed the presence of many tiny particles of organised structure, such as "ceils with bordered pits" and fragments of medullary rays so characteristic of Coniferous or Pine wood, and of Pine wood only, as used in the shaft timbering. At the close of the lecture, Dr. Fred E. Wright, of the Carnegie Institution of Washington, U.S.A.. contributed some remarks and indicated the wide interest and importance of the observations made by Mr. Parry. BRITISH ASSOCIATION FOR THE (Continued from Page 247.) It seems to me, then, that we must ccgard Mersenne's assertion as exploded; and for my part it interests me no longer. If he is wrong about 89 and 107, I do not care greatly whether he is wrong about 137 as well or not, and I should regard the computations necessary to decide largely wasted. There are so many much more profitable calculations which a computer could undertake. as very I hope that you, will not infer that I regard the problem of perfect numbers as uninteresting in itself; that would be very far from the truth. There are at least two intensely interesting problems. The first is the old problem, which so many mathematicians have failed to solve, whether a perfect number can be odd. The second is whether the number of perfect numbers is infinite or not. If we assume that all perfect numbers are infinite, we can state this problem in a still more arresting form. Are there infinitely many primes of the form 2" 1? I find it hard to imagine a pro ›lem more fascinating or more terribly difficult than that. It is plain, though, that this is a question which computation can never decide, and it is very unlikely that it can ever give us any data of serious value. And the problem itself really belongs to a different chapter of the theory, to which I should like next to direct your attention. 4. Are there infinitely many primes of the form n2 + 1? Let me first remind you of some well-known facts in regard to the distribution of primes. There are infinitely many primes; their density decreases as the numbers increase, and tends to zero when the numbers tend to infinity. More accurately, the number of primes less than x is, to a first approximation, x 2 dt log t gives a very good approximation to the number of primes. This number differs from Li x by a function of a which oscillates continually, as Mr. Littlewood, in defiance of all empirical evidence to the contrary, has shown, between positive and negative values, and is sometimes large, of the order of magnitude √ or thereabouts, but always small in comparison with the logarithm-integral itself. Except for one lacuna, which I must pass over in silence now, this problem of the general distribution of primes, the first and central problem of the theory, is in al! essentials solved. But a variety of most exciting problems remain as to the distribution of primes among numbers of special forms. The first and simplest of these is |