July 13, 191 1] 



NATURE 



45 



all the masts are distinctly visible, pronounced white flares 

 extending skywards. The photographs were taken on a 

 Kodak film, exposure about one twenty-fifth of a second. 



On the Tuesday the wind was blowing fresh from the 

 north-west, and on the Wednesday the wind was still 

 fresher from the south-west. 



This note and photographs are being sent with the object 

 of directing attention to the phenomenon, and with the 

 hope of learning whether it has been noticed by others. 



Arnold Spiller. 



Northumberland Yacht Club, Blvth, July 5. 



Anhydrous Volcanoes. 



The cumulative evidence in Dr. Albert Brun's " Re- 

 cherches sur l'exhalaison volcanique " leaves very little 

 (loulii Imt that the explosive action in volcanoes is due to 

 decomposition of compounds of C, N, CI, F, &c, held 

 Dissolved in the glass of the lava. All the theories about 

 volcanic activity must be, revised, as pointed out by that 

 author ; but along with .the disappearance of the theory 

 attributing the explosive action to water, there must be a 

 lisappearance also of the theory of a hot interior of the 

 globe, as a corollary following on Dr. Brun's researches, 

 if on no other grounds. For if a magma containing 

 carbides, nitrides, &c, will explode with great violence if 

 heated, then, supposing the earth's centre were hot, a 

 single volcanic vent would allow the whole of the 

 volcanic magma contained in the earth to swell and boil 

 over on to the surface of the earth. 



Accepting, then, Dr. Brun's conclusions, the volcanic 

 magma below the crust must be cold, and only when heat 

 is applied to it, through movements in the earth's crust, 

 will the expansion take place and the volcano be formed. 

 The gases given off from volcanoes, or expelled by heating 

 obsidians to their melting points, are strongly reducing, 

 and were, therefore, forced into the magma at a stage in 

 the earth's growth (on the planetismal hypothesis) when 

 the surface was incandescent from the infalling of 

 meteorites, and when the atmosphere consisted of gases 

 carried to the earth in these meteorites, principally CO, 

 CO,, II, N, and CH,. The rock-silicates absorbing these 

 gases gradually cooled down and were buried, and thus a 

 supply of material was laid by from which the volcanoes 

 of future ages could be formed. The absorption is more 

 than mere occlusion, for an obsidian can be thoroughly 

 weathered and absorb water throughout its mass, yet, when 

 dried and then raised to fusion point, free chlorine can be 

 given off, showing that the water cannot have had access 

 to the storage chamber of the chlorine. Again, a granite 

 powder may be sprayed with paraffin and heated to 

 1100 C. The excess of paraffin burns instantly, but a 

 certain portion is fixed by the silicates and remains as 

 paraffin within the rock-magma up to the explosion point, 

 when it is expelled with explosive violence. Actual paraffin 

 can be distilled from the pitchstone of Arran. If 

 paraffin can be retained in a magma heated to above 

 1000 C, it means that it has practically entered into 

 chemical composition with the silicates. 



An obsidian retains some of the gases originally held in 

 the magma, because it has cooled quickly ; a certain time 

 is necessary, even at fusion point, for the gases to be 

 expelled ; hence a lava will continue to give off gases as it 

 flows down the side of the volcano, although a large 

 proportion has escaped in the chimney, and will still be 

 found to contain gas when it has cooled completely. The 

 solidified lava, if left long enough, will slowly give off 

 gases, N, CI, CO, CO,, CH„, &c, but the life of a lava, 

 before it becomes what Brun calls a " dead rock," is 

 probably thousands of years. 



There is certainly an analogy, if nothing more, between 

 these results of Dr. Brun's researches, and the properties 

 of radio-active substances. Helium must have existed in 

 the earth's atmosphere when the surface was incandescent, 

 for the same reason that it exists in the sun's atmosphere 

 to-day, and it is possible that certain substances had the 

 power of causing it to enter into a sort of chemical com- 

 bination with them, like the paraffin in the rock silicates. 

 Existing in the lower layers of the earth's crust near the 

 centre, which I have given reasons to suppose is verv little, 

 if at all, above the temperature of outer space, these 



NO. 2176, VOL. 87] 



substances would retain the helium frozen in them, as the 

 chlorine, paraffin, &c, are frozen in the rock silicates, and 

 they could retain the helium for indefinite periods. When 

 some of these substances, however, are brought by the 

 ordinary processes of ore-formation into the warmer 

 regions of the outer crust, they would give off their 

 helium. The difference between the way in which the 

 helium is held in radio-active substances, and that in which 

 the gases are held in rock-silicates, is shown by the fact 

 that the rate of expulsion of helium is unaffected by 

 temperatures available in the laboratory, whereas the gases 

 can be all driven off from a rock-silicate at one time. 

 There may be nothing in this, but it may reassure some 

 who are alarmed at the rate of decay of radium and 

 see no possible sources of replenishment. 



Ernest H. L. Schwarz. 

 Rhodes University College, Grahamstown, June 12. 



The End of the Beagle. 



With reference to the letter in Nature of June 1, the 

 following particulars of what 1 know upon the subject 

 may be of interest. 



In the year 1863, at Hong Kong, a friend of mine 

 purchased from the Government the dispatch gun vessel 

 Beagle, which was at that time laid up, after being some 

 years on the China Station. We had her thoroughly over- 

 hauled and repaired, and renamed her The Stork (a 

 sacred bird of the Japanese). I then took her over to 

 Japan, to the ports of Nagasaki and Yokohama, for sale. 

 She was visited and examined by the Japanese ; but no 

 sale was effected at the time, and I took her back to 

 Shanghai. However, she was eventually purchased by the 

 Japanese Government, and after that I have no further 

 knowledge of her movements. 



The other Beagle mentioned in Nature was an old 

 10-gun sailing brig, and I think there can be no doubt 

 that she was the vessel in which Darwin made his scientific 

 explorations. I see in the " Encyclopaedia Britannica " 

 that Darwin made his voyage in the Beagle in the years 

 1832 to 1836, several years before the Beagle that I com- 

 manded was built, so I presume that settles the matter. 

 H. C. Shoosmith. 



54 Billing Road, Northampton, June 23. 



[The second line of the " Voyage of a Naturalist " 

 describes the Beagle as a 10-gun brig. The vessel was 

 barque-rigged, and is believed to have been about 280 tons. 

 — Ed. Nature.] 



The Osmotic Pressure of Colloidal Salts. 



In reference to the interesting letter of Dr. Hardy, pub- 

 lished in Nature of June 29, I should like to state that 

 work on similar lines has been proceeding in this labora- 

 tory during the last year and a half. We have been 

 investigating the general subject of " membrane-equilibria " 

 and " membrane-potentials " in the case of non-dialysing 

 electrolytes. An informal note on the principles involved 

 in these investigations was read by me before the Physio- 

 logical Society in December, 19 10. Some time ago a 

 paper dealing with the theory of these equilibria and 

 potential-differences was sent to the Zeitschrift fiir 

 Elektrochemie. In this paper, which is already in type, 

 Dr. Hardy will find that I have arrived at equations 

 expressing the membrane-potentials which are practically 

 identical with the equation given in his letter. We propose, 

 therefore, to continue our investigations on the subject. 



F. G. DONNAN. 



Muspratt Laboratory of Phvsical and Electro- 

 chemistry, University of Liverpool, July 1. 



The Date of the Discovery of the Capillaries. 

 Dr. Fraser Harris is quite correct in stating that 

 Malpighi (working with Charles Fracassati) demonstrated 

 the existence of blood capillaries with the microscope in 

 the year 1660. The two letters to Joh. Alph. Borelli 

 announcing the discovery were published in folio at 

 Bononia (Bologna) in 1661. This is now a rare tract, and 

 not usually quoted. It is, however, doubtful whether 



