December [3, 1894J 



NA TURE 



151 



— he does not follow up the first statement by including 

 it in his list of reputed poisons (vol. vi. p. 309.) 

 It may be added that Dr. Watt's selection of authorities, 

 generally, appears to be somewhat capricious. He does not 

 appear to be acquainted with Garcia de Orla's famous work on 

 Indian drugs, for he gives Linschoten and others credit for 

 observations not originally made by them, but by Garcia, e.g. 

 art. Miinna. 



Again, when writing of ambergris, surely he might have found 

 some more direct source of information regarding a product 

 derived from whales, than a work, excellent though it be, 

 which deals properly with the products of the Punjab. 



I write as one not wishing to find fault, especially as I recog- 

 nise the good services done by Dr. Watt, but because I believe 

 such a work so brought out, should be a faithful .■nummary of 

 recorded facts, which, if hitherto only known to comparatively 

 few, should be so stated as not to mislead the many who may 

 have occasion to refer to the Dictionary. V. Ball. 



Science and Art .Museum, Dublin, November 19. 



Drift-Bottles in the Irish Sea. 



In Nature for Nov. 8 (p. 35) mention is made of the travels 

 of some drift-bottles in the south seas. It maybe of interest 

 to put on record the results so far obtained of the distribution 

 of bottles set free by the Liverpool Marine Biology Committee 

 in order to get further information in regard to those currents 

 in the Irish Sea which would affect small floating bodies. The 

 objects we have had in view are : (l) A purely scientific matter, 

 the source and distribution of the plankton ; and (2) the probably 

 utilitarian object of determining the movements of the food 

 of fishes, and so one of the causes of their migrations, and also 

 the drift of the floating ova and embryos of food fishes. The 

 tidal currents of the area in question are to a considerable ex- 

 tent known, and marked on the charts and given in books on 

 " Sailing Directions"; but to these currents have to be added 

 the modifying influence of prevalent winds, and what we want 

 to get at is the resulting average effect. We want to know in 

 what direction an object set floating at any spot will probably 

 be carried at various times of the year in ordinary weather. The 

 surface organisms are such feeble swimmers, if locomotory at 

 all, that any results obtained from small floating bottles may 

 reasonably enough be regarded as holding good for the plankton. 



The form of bottle we have chosen is cheap, buoyant, strong, 

 and well corked. It measures 7 5 cm. in length over all, and 

 I -8 cm. in diameter. Inside it is placed a printed paper re- 

 questing the finder to fill in date and locality, in spaces left for 

 the purpose, and post it back to myself. The papers are 

 numbered, and are folded in the bottle in such a way that the 

 distinguishing numbers can be read through the glass, so as to 

 ensure that the bottles are set free in consecutive order. After 

 the bottle has been corked up, the end is immersed a couple of 

 times in melted paraffin, so as to close up the pores in the cork. 

 None of the papers that have been returned show signs of 

 water having got into the bottles. 



As to the distribution, I sent off the first few dozen myself 

 from steamers crossing between Liverpool and the Isle of Man, 

 dropping a bottle over every fifteen or twenty minutes between 

 the Bar and Douglas, and also from a steam-trawler while 

 dredging between Port Erin and Ireland. Mr. A. Holt has 

 had a number of bottles distributed for me from his outward- 

 bound steamers on their course between Liverpool and St. 

 George's Channel, and from the Mull of Galloway round to 

 theMcisey, The Lancashire Sea-Fisheries steamer has set free 

 another series along various lines up and down the Lancashire 

 coast, and finally some have been set free at equal intervals of 

 time during the rise and fall of the tide from the Morecambe 

 Bay Light vessel in the northern part of the district, and from 

 the Liverpool Northwest Light vessel in the southern pan. 

 The distribution has now been going on since the beginning of 

 October, and a very fair proportion (about one out of every 

 three) of the papers have already been returned to me duly 

 filled in and signed. They have come from various parts of the 

 coast of the Irish Sea — Scotland, England, Wales, Isle of Man, 

 and Ireland. Some of the bottles have gone quite a short 

 distance, having evidently been taken straight ashore by the 

 rising tide. Others have been carried an unexpected length — 

 f i'. one (No. 35) set free near the Crosby Light vessel olT 

 Liverpool at 12.30 p.m. on October I, was picked up at Salt- 

 coals in Ayrshire on November 7, having travelled a distance 



NO. 13 II, VOL. 51] 



of at least iSo miles (probably far more) in 37 days or less ; an- 

 other (H 20), set free near the Skerries, Anglesey, on October 

 6, was picked up at Ardrossan, Ayrshire, on November 7, 

 having gone at least 150 miles in 31 days. 



It would be premature as yet, until many more dozens or 

 hundreds have been distributed and returned, to draw any very 

 definite conclusions. It is only by the evidence of large 

 numbers that the vitiating effect of exceptional circumstances, 

 such as an unusual gale, can be eliminated. However, I may 

 state, as provisional results so far, that nearly fifty per cent, of 

 the bottles found have been carried across to Ireland, and they 

 are chiefly ones that had been set free in the southern part of the 

 district (between Liverpool and Holyhead) and ofi" the Isle of 

 Man. The bottles set free along the Lancashire coast and in 

 Morecambe Bay seem chiefly to have been carried to the south 

 and west — to about Point of Ayre, in North Wales, and Douglas, 

 in Isle of Man. It is apparently only a few that have been 

 carried out of the district through the North Channel. The 

 most interesting point, so far, is that so many of the bottles have 

 been stranded on the Irish coast, although they were sent off 

 for the most part much nearer to the English and Welsh coasts, 

 showing no doubt the influence of the spell of easterly winds 

 in October. W. A. Herdmam. 



University College, Liverpool, November 29. 



The Explosion of Gases in Glass Vessels. 



When Prof. Lothar Meyer was visiting Manchester a few 

 years ago (on the occasion of the meeting of the British Associa- 

 tion), he surprised me by saying that it was his custom in lecture 

 to explode mixtures of ethylene and other hydrocarbons with 

 oxygen in glass cylinders, some 10 to 12 inches long by li to 

 2 inches in diameter (if I remember rightly), and that he had 

 never had an accident. I suppose I did not sufficiently conceal 

 my surprise, for he immediately demanded that we should go 

 to the laboratory and repeat the experiment. Not having a 

 mixture of ethylene and oxygen ready, I could not accept the 

 challenge on the spot. The issue was therefore changed. 

 Prof. Lothar Meyer said that lie would fire a mixture of hydro- 

 gen and oxygen in a thin glass test-tube without breaking it. I 

 confess I was sceptical, until I saw him do it time after time 

 without injury. He argued that if the thin test-tube would 

 withstand the explosion of hydrogen and oxygen, a thick glass 

 cylinder would withstand the more violent explosion of a hydro- 

 carbon. Nevertheless I ventured to warn him against trying 

 the experiment with either acetylene or with cjanogen, the two 

 gases I had found to explode more violently than any others, 

 specially wilh a small quantity of oxygen. Prof. Meyer's 

 recent accident with acetylene and oxygen has led him to warn 

 chemists against the danger of that mixture. I would wish to add 

 to that warning that the danger is equally great, if not greater, 

 with a mixture of cyanogen and oxygen. 



Prof. Lothar Meyer asks how we can account for the violence 

 of the explosion of acetylene, when the velocity of its explosion 

 is so little greater than the velocity of explosion of marsh gas 

 and of ethylene, while it is far less than that of hydrogen? It 

 is important to bear in mind that the explosion-wave is not set 

 up at once ; when a gaseous mixture is ignited at the open end 

 of a tube the flame starts comparatively slowly. The violence 

 of an explosion in a short tube depends mainly on whether the 

 explosion wave is set up or not. I think the immunity 

 so long enjoyed by Prof. Meyer's cylinders depends on the 

 fact that the wave was not set up. I have found that pieces 

 of strorg combustion tubing, which will stand an hydraulic 

 pressure of twenty-five atmospheres, are broken by the ex- 

 plosion-wave of hydrogen and OX) gen. It requires exception- 

 ally strong glass tubes, capable of bearing at least 120 atmo- 

 spheres, to withstand the shock of the explosion-wave with 

 cyanogen or acetylene. With both these gases it is the incom- 

 plete combustion which occurs with the greatest rapidity and 

 violence. According to the hypothesis I have published, viz. 

 that the explosion-wave travels with the velocity of sound in 

 the burning gases, the pressures existing in the explosion-wave 

 of cyanogen and acetylene with their own volume of oxygen 

 are 1 17 and 105 atmospheres respectively. <^uite apart Irom 

 this hypothesis, the pressures may be calculated from Riemann's 

 equation for the propagation of a wave of constant type, since 

 we know the density of the unburnt gases and the rate of pro- 

 pagation of the wave. According to Riemann's equation the 

 pressure in the cyanogen explosion is 140 atmospheres, and in 



