JrLY 1, 1898.] 



KNOWLEDGE. 



151 



That they lie at the bottom of the matter — that phos- 

 phorescence is due to their presence — has been and can be 

 proved in several rather pretty ways. It is not sulScient, 

 of course, that we should always detect them in any 

 examination of luminous sea- water; to prove that they are 

 the cause of light we must be able to procure luminosity 

 by introducing them into water that did not previously 

 show this quality, and this can be done thus ; — 



Place a few of these tiny organisms into sea-water or 

 broth prepared from fish, and Iceep at a suitable tempera- 

 ture ; they can then be cultivated without much ditliculty, 

 and as they spread and develop phosphorescence appears, 

 so that a removal of the vessel into another room shows 

 unmistakably the glow of the familiar li,L;ht. It only 

 appears, however, at the surface of the liquid, where the 

 oxygen of the air has free access to the bacteria ; if, for 

 experiment's sake, the supply of fresh air be cut off — that 

 is, if no oxygen be allowed to come near them^then the 

 little colony of bacteria loses its fascinating power and 

 remains dull and shorn of its glory. But restore the air, 

 and the microbes again recover their normal condition and 

 luminosity seems a natural corollary. There is a tale 

 told that a lady, whose husband made bacteria his study, 

 took a leaf out of his book, and cultivated these bacteria on 

 gelatine in such a way that as they developed they shone 

 out the message, " Hommage a M. Pasteur." The shining 

 letters were then photographed and the picture sent to 

 the great bacteriologist, thus conveying in graceful form 

 the warm appreciation in which he was held by those 

 following in his steps. 



The explanation, too, of the luminous shoals of fish is 

 now made plain, and we can apparently get " fiery 

 herrings " at will. No longer are we to believe that the 

 herrings themselves, by the exercise of some marvellous 

 power, or by the excretion of an extraordinary substance, 

 give rise to the striking luminosity, but rather that their 

 brightness is due to myriads of these infinitesimal bodies, 

 which cling to their surfaces and invest them in a coat of 

 shining light. Thus, if some herrings, newly caught, and 

 with the sea-water still fresh on them, be placed on one 

 plate and covered down with another, and then put into a 

 suitable temperature and left for a day and a night, glints 

 of light can, at the end of the time, be detected at various 

 points on their bodies when they are examined in a dark 

 room. If they are yet again put away for another twenty- 

 four hours, the points of light spread until the whole ol' 

 the fish are enveloped in a beautiful bluish glow. The 

 light is then at its best, and gradually fades away as the 

 fish putrefies and the sea-water dries up. If a little of 

 the light-giving matter be scraped ofl' the skins of the 

 herrings and examined under the microscope, it shows 

 itself to be nothing but colonies or collections of bacteria, 

 all living at a great pace, dividing, multiplying, ami 

 developing at a tremendous rate. Each member of a 

 colony is normally roundish in shape, but in this stage of 

 reproduction it is continually elongating into a long ellipse, 

 a constriction appears at the middle, and it divides into 

 two. Eacli of these two in their turn elongate, become 

 constricted, and divide. And so it goes on, the process 

 being often so rapid that short chains are formed, the 

 various portions being unable to break away in time. The 

 particular bacterium which affects herrings and cod is 

 remarkable for its great luminosity ; in fact, it exceeds all 

 other species in this quality. 



It is a curious fact that the addition of a little sugar to 

 the liquid or the gelatine on which these phosphorescent 

 bacteria are being cultivated increases very much their 

 power of producing light ; the sugar must, however, be 

 used with great moderation, as too much of it has a con- 



trary effect and checks the luminosity altogether. The 

 reason for this is that nearly all this class of bacteria 

 require carbon as nourishment if they are to develop to 

 their highest powers. Like much of the food we eat, it is 

 not essential to them ; they can manage very well without 

 it, but they are all the better for having it. Now sugar is 

 very largely composed of carbon ; hence the good results 

 which follow its presence. Glycerine, which is of similar 

 composition, will do almost as well ; from both bacteria 

 can easily withdraw carbon. Two photo-bacteria have, 

 however, been observed which are somewhat differently 

 constituted ; one is found round the West Indies and the 

 other in the North Sea, and neither apparently requires 

 sugar or glycerine in any form — in fact, either of these 

 substances, even in the smallest quantity, appears to be 

 directly injurious. But why this should be so it is not 

 easy to define. 



A Dutchman named Beyerinck lias lately made a special 

 study of these photo-bacteria, and has experimented with 

 them in a great number of ways to determine, if possible, 

 why they should thus become illuminated, and if the light 

 plays any notable part in their life history ; but his results 

 are, seemingly, all more or less of a negative nature. 

 He cannot find that it has any very important function. 

 The breathing of these tiny organisms is not, apparently, 

 in anyway bound up with it ; their nutrition, growth, and 

 development go on quite well even if they are placed 

 under such conditions that their luminosity is arrested ; in 

 no way, indeed, is it a vital process. It only seems to 

 depend on the food which the bacteria feed upon and the 

 presence of oxygen. Given suitable food and plenty of 

 fresh air, and they exhibit their characteristic light ; deprive 

 them of one or the other and they no longer shine. 



This knowledge helps us to understand, then, the 

 phenomenon of phosphorescence. It is visible only at 

 night because in the full glare of day the greater light 

 overpowers the lesser ; it is visible at certain times and 

 seasons because the conditions are such as to evoke it. 

 And what is favourable for the Lighting up of a single 

 bacterium is favourable for all ; hence the myriad multitudes 

 of infinitesimal units, each set glowing with its tiny light, 

 is sutficient in the sum total to put a whole ocean aflame. 



It would, of course, be presumptuous, and doubtless 

 erroneous, to say that all the phosphorescence of the sea 

 is due solely to photo-bacteria ; it can only be asserted in 

 the present state of our knowledge that they are certainly 

 responsible for a great share of it. But this wonder of 

 nature must now be regarded as yet another instance of 

 the mighty results accomplished through the agency of 

 the smallest of living things. 



THE PETROLEUM INDUSTRY.-II. 



By George T. Holloway, assoc. r.c.s. (lond.), f.i.c. 



IN the earlier days of the petroleum industry the crude 

 oil was carried from the wells to the refineries in 

 barrels containing forty-two American gallons, at 

 such heavy expense as to enormously increase the 

 cost to the consumer. By land the barrels were 

 conveyed on rough waggons over the almost roadless tracts 

 where the oilfields were mainly located, while, where 

 river transport was possible, barges were used as the 

 vehicles of transportation. In 1862, however, a branch 

 railway was carried into the oil regions of Pennsylvania, 

 and in 1866 railway tank waggons were introduced. At 

 first constructed of wood, and having a capacity of about 

 two thousand gallons, these waggons were soon replaced 

 by the boiler- iron tanks with which we are now familiar. 



