Aug. I, 1872] 



NATURE 



261 



must be some connection between the two classes of phenomena. 

 The nature of this connection has been diflferently explained by 

 clirferent writers. But the purpose of this note is not to criticise 

 existing theories, but to propose one, which I believe to be new, 

 and to be capable of explaining why a sudden volcanic eruption 

 must ordinarily be accompanied by earthquake shocks of greater 

 or less \iolence (not necessarily always sensible), and why earth- 

 quakes may occur without any contemporaneous outburst. ! 



In the preface to his " Physikalische GeoloLjie," Bischof 

 suggests that the phenomena observed in the laboratory should 

 be taken as our guides to explain what happens in nature. Let 

 us see, then, if in the laboratory we meet with any phenomena 

 analogous to volcanoes and earthquakes. 



When a reaction has to be performed in a sealed tube, and it 

 is expected that much gas will be evolved, and consequently the 

 pressure in the tube be much increased, it is one of the com- 

 monest precautions to draw out the tube to a capillary orifice 

 before closing it. When this precaution has been neglected, 

 and even although the point be allowed to blow itself out in the 

 llame of a lamp, an explosion not unfrequently attends the at- 

 tempt to open it. Let us consider the circumstances. 



We have a tube whose walls are being pushed out by a very 

 high pressure from v, ithin, which, Iiowever, it resists ; but at 

 the moment that this pressure is suildenly relieved at one point, 

 the tube bursts. What is the cause of the explosion ? It clearly 

 cannot be the mere reduction of pressure. As long as the pres- 

 sure was equally distributed oi-er the walls of the vessel, we have 

 seen that it was successfully resisted ; as soon, however, as it 

 was suddenly relieved at one point, a great ineciuality in the ten- 

 sion of the gas in the immediate vicinity of this point would be 

 the result, the gas immediately at the opening assuming at once 

 the atmospheric pressure, while that at, say, the eighth of an 

 inch from it is at the tension of the gas in the tube. The prac- 

 tical effect of this sudden inequality of pressure would be to pro- 

 duce a tug on the mass of elastic fluid, which would cause the 

 walls momentarily to tend to collapse, and this tendency to 

 collapse would be transmitted through the glass as a wave. This 

 wave would to a certain extent distort, and therefore weaken, the 

 walls ; and consequently, if the pressure inside were great 

 enough, it would burst them ; if not, the only effect would be 

 that a shock would traverse the walls of the vessel, and the 

 pressure would relieve itself by the orifice. 



Now, suppose the vessel to be a subterraneous cavity contain- 

 ing an atmosphere of very great tension, and that suddenly the 

 envelope gives way at one point, what will be the result? Just 

 as in the case of the glass tube, the sudden relief of pressure will, 

 in the way indicateil above, cause the walls to experience a 

 momentary collapsing impulse, which will be propagated as a 

 wave until extinguished by the imperfect elasticity of the crust. 

 The sudden outburst will be a volcanic eruption, and the conse- 

 quent collapsing shock will be an earthquake, which either will 

 or will not be accompanied by rending of the crust, according to 

 the strength of the walls and the greatness of the pressure. 



It is, however, not necessary that there should be a visible 

 volcanic eruption. For, suppose two such subterraneous cavities 

 at different pressures, separated from one another by a wall 

 weaker than that which separates either of them from the outside 

 of the earth ; then, if the pressure in the one becomes so great 

 as to burst the barrier between the two, the result will be an 

 earthquake. And similarly, the pressure in the two thus united 

 cavities may go on increasing until they burst into a third, and 

 so on until they come to a vent, which is either open or weak 

 enough to yield to the pressure. In this way an earthquake and 

 an eruption may be in intimate connection with one another, 

 although a considerable interval of time intervene between the oc- 

 currences, and the localities affected be at great distances from 

 each other. And it is possible that some connection of this 

 kind may have existed between the earthquake of Antioch and 

 the eruption of Vesuvius, both having been extreme in their 

 violence. Indeed, the \\ hole scries of disturbances, commencing 

 with the earthquake in California and terminating with the erup- 

 tion of Vesuvius, noticed by Mr. Corfield in Naturi-; of May 23, 

 may f ossibly find an explanation under this theory. 



The effect of sudden relief of pressure in weakening the walls 

 of vessels explains many cases of explosion which otherwise 

 ajjpear anomalous. Thus, high-jiressurc boilers have been 

 frequently olserved to burst at the moment when the engineer 

 turns on the steam. 



In conclusion, the above sketched theory assumes nothing but 

 what we know to be fact. We know that, at least in the neigh- 

 bourhood of volcanoes, there must be subterraneous cavities whose 



atmosphere is at an exceedingly high-pressure, for we not only 

 see it emitted from the vent, but it projects enormous masses of 

 rock high into the air, thus testifying to the energy with which 

 it was endowed. Further, gi\'en this high-pressure atmosphere, 

 it is certain that, on its being suddenly relieved, it would com- 

 municate a shock to the crust, and this, on being felt outside, 

 would be described as an earthquake. I think it is therefore 

 clear that some earthquakes must be produced in this way. 

 Of course this does not include the possibility of there being 

 other causes of concussion which might produce similar effects. 

 Edinburgh, June 10 J. V. Bucn.^N-'iN 



On the Cohesion of Figures of Creosote, Carbolic and 

 Cresylic Acids 



With reference to the note by Mr. J. H. Spalding contained 

 in NATUiiE of June 13, I am reminded by my friend Mr. 

 Rodwell that some five or six years ago I showed him the cohe- 

 sion figure of carbolic acid. A crystal of this acid was t.aken up 

 on the end of a platinum spatula, and gently delivered to the 

 surface of clean water contained in a clean glass ; the crystal 

 gave a few jerks, then suddenly liquified, and displayed its highly 

 characteristic figure so well described by your correspondent. I 

 may further remark that I showed this figure in the chemical sec- 

 tion of the British Association, at Manchester, in September 

 lS5i, and a drawing of it is given in the plate which accompa- 

 nies my paper in tlie Pliilmophkal Magazine for October of 

 that year. In this paper it is described as " an exaggerated form 

 of the figure of creosote ; tlie water seems to tear it to pieces ; 

 the crispations are amazingly active, and the disc quickly breaks 

 up and disappears. Indeed, while a drop of creosote will endure 

 five minutes on the surface of an ounce of distilled water in a 

 small gl.iss, a drop of carbolic acid will last only a few seconds 

 on the same quantity of water. The cohesion figure is however 

 quite characteristic of the substance, and cannot be for a moment 

 mistaken for any other substance that I have examined." 



Creosote, carbolic and cresylic acids, and newly-distilled oil of 

 cloves, give remarkable figures of the same type, each of which 

 is characteristic of the substance. 



Mr. Spalding remarks that warm water destroys all action, by 

 lessening, as he supposes, the adhesion of the liquids. I am 

 sorry to have to object to this remark, but I have no doubt that 

 Mr. Spalding was led to make it by employing unclean water 

 or an unclean recipient. If distilled or even ordinary tap water 

 be heated over a spirit lamp in a clean flask, and be poured into 

 a clean vessel, the surface of the water is active at dU degrees 

 between the temperature of the air and just below boiling. On 

 the surface of cold water a drop of creosote passes through the 

 following changes: — (i) As soon as the drop is placed on the 

 surface of the water the figure is formed for an instant ; (2) it 

 splits open and forms a kind of brittle arc, which (3) is shivered 

 into a number of separate discs, each of which is a perfect co- 

 hesion figure of creosote. These figures perform their evolutions 

 independently of each other, sailing about with rapidity, but 

 never clashing with or disturbing each other. In the Philoso- 

 pli'ual Maga-Jne for June 1S67, figures are given of these diffe- 

 rent phases of the figure. 



Now, if the water be heated to 100° Fall., or from that to 

 150°, a drop of creosote deposited on its surface produces a good 

 active figure, but it does not split open or form the brittle arc 

 above referred to ; it sails slowly over the surface, firing off volleys 

 of small globules in radial lines, and only when much wasted 

 does it split into smaller systems. All this is what might be 

 expected from the diminished surface-tension occasioned by the 

 heat. Indeed, it is a beautiful illustration of the slight diminu- 

 tion of surface-tension in hot water as compared with cold. In 

 consequence of not splitting open, the duration of the figure is 

 greater on the surface of hot water as compared with cold. 



Carbolic and cresylic acids are also very active on hot water, 

 at all temperatures up to 210° Fah. C. Tomlinson 



Highgate, N. 



Hereditary Instinct 



Will you allow me to recount to your readers what appears 

 to me to be a striking instance of the transmission of impression 

 in animals ? 



A few years ago I bought in Skye a perfectly uneducated Skye 

 terrier. The first accomplishment which I taught him was 



