2,^^ 



NATURE 



[August 6, 1891 



was covered by a thick coating of dust and sand, upon 

 the surface of which were the usual white and yellowish- 

 green chloride crusts seen on such occasions, so rich in 

 copper as to plate with that metal the iron nails of our boots. 

 The crater had considerably enlarged, the edges were in 

 an extremely unstable state, with often considerable 

 strips marked off by cracks parallel to the free edge, so 

 that, with a slight push by a stick, it was possible to 

 detach large masses of the materials which form the sides 

 of the crater in the recent cone of eruption. So danger- 

 ous were the edges, that it was but in two places that my 

 experience indicated as being safe to approach and look 

 over, and that even with several precautions ; so that the 

 fatal accident to Seiior Silva Jardim, who lost his life 

 here but a few hours after our departure, is not to be 

 wondered at. 



On looking down some 45 to 50 m. beneath us, we 

 could see the glow from a mouth some 2 or 3 m. in 

 diameter. The walls of the crater were concave, so that 

 although overhanging at the top, yet a plumb-line let fall 

 from the edge would strike the bottom of the cliff. The 

 crater bottom was roughly plain, due to the combination 

 of a talus all round, and an attempt at a cone encircling 

 the main vent. It will be thus seen that the crater cavity 

 was of the form of a convex-sided cylinder, or more simply 

 barrel-shaped, with its upper diameter some 50 to 55 m. 



With much difficulty we made our way around to the 

 north side of the cone of eruption, which had now lost its 

 usual loose scoria surface, which was buried beneath a thick 

 coat of sand and dust, covered with a thin saline crust on 

 its surface. The upper limit of the radial rift, which we 

 were prevented from examining three weeks previously, 

 on account of its giving out so much vapour as to consti- 

 tute the temporary escape aperture of the volcano, had 

 now become quiescent, so that we could fully examine it. 

 Oiily a current of hot air was now issuing from it, but I 

 was able to collect some fine masses of crystallized 

 molysite and kremersite from its edges. Its average 

 breadth was about o'5o m., where it traversed old com- 

 pact lava, but of course it disappeared as soon as it 

 reached the looser materials. The real azimuth of its 

 orientation, which we could now determine with greater 

 accuracy than when we were walking over hot rock and 

 enveloped in hot irritating vapours, proves to be, as it 

 radiates away from the axis of Vesuvius, about 15° west 

 of north. It curves then a little to the north, and near 

 the foot of the great cone it again assumes nearly the 

 same azimuth as at starting, an arrangement which is 

 quite evident when the Vesuvian cone is regarded from 

 the Punta del Nasone. From that, the highest point of 

 Somma, the lower extremity of the rift lies a little to the 

 right or west, and faces that part of the Somma ridge 

 which corresponds to the upper extremity of the Vallone 

 Cancherone. 



In the forenoon of June 30 much dust had fallen at the 

 lower railway station, of which we collected some bags- 

 ful. It is the usual fine sandy material of these erup- 

 tions, and consists of the pulverized materials of the cone 

 of eruption. 



Having passed the night at the lower railway station, 

 the next day we crossed the Atrio, ascended to the western 

 extremity of the ridge of Somma, and followed it along ; 

 so as to get a general bird's-eye view of the whole scene 

 of the eruption, and take photographs of the more im- 

 portant points. As one stands on the Punta del Nasone 

 and embraces that magnificent view of Vesuvius and 

 the Atrio del Cavallo, one sees at their feet the new 

 lava-stream in the form of the letter ^, the hori- 

 zontal portion of which is still being prolonged down 

 the Atrio towards the Fossa della Vetrana. In the 

 middle of the ridge we found a thin coating of 

 fine red dust which had reached thus far from the 

 crater. Much of the Atrio was also covered by the same 

 material. Scaling the cliff face just beyond the Cognulo 



NO. 1 136, VOL. 44] 



di Otfajano to the Atrio del Cavallo, we again visited the 

 lower point of the outburst. Most of the beautiful fuma- 

 roles were in a state of ruin, and lined by good-sized 

 crystals of haematite and mixed chloride crusts. Here 

 the lava was quite solid, though at one point was a hole, 

 some 50 m. from the base of the great cone, where we 

 could see the molten rock flowing lazily along about 

 a metre beneath our feet. The lava at the end of the 

 flow was making considerable progress to the westwards, 

 and stood opposite dyke 13. 



Since then, few changes have taken place in the moun- 

 tain : the crater still gets larger, dust is thrown out, and 

 the lava descends. These phenomena are capable of 

 continuing for months if the drainage opening does not 

 enlarge. 



As the eruption progresses, I will send you further 

 details. H. J. Johnston-Lavis. 



THE PRODUCTION OF MUSICAL NOTES 

 FROM NON-MUSICAL SANDS. 



n^HAT I have succeeded in producing musical notes 

 -*• from sand that was never before musical, and am also 

 able to produce similar results from certain mute or "killed'' 

 musical sands which have been temporarily deprived of 

 their musical properties, has already been announced in 

 the Chemical News (vol. Ixiv. No. 1650). 



It is not necessary now to give the details of the 

 numerous experiments which led up to this discovery ; 

 it will be, perhaps, sufficient for present purposes, to 

 state that in November 1888 I published a paper ^ in 

 which I propounded a theory to account for the cause of 

 musical sounds issuing from certain sands. After giving 

 various reasons for my conclusions, I said : — " Itoccurrea 

 to me, then, that the music from sand was simply the 

 result of the rubbing together of the surfaces of millions 

 of perfectly clean grains of quartz, free from angularities, 

 roughness, or adherent matter, in the form of clinging 

 fragments investing the grains, and that these microlithic 

 emissions of sound, though individually inaudible, might 

 in combination produce a note sufficiently powerful to be 

 sensible to us." 



Having described numerous experiments, and drawn 

 attention to the hopeful results obtained from the " millet- 

 seed" sand, my paper concluded with the following: — 

 " From what I have now told you, I think we may con- 

 clude that music may be produced from sand if (1) the 

 grains are rounded, polished, and free from fine frag- 

 ments ; (2) if they have a sufficient amount of 'play' to 

 enable them to slide one against the other ; (3) if the 

 grains are perfectly clean ; and (4) if they possess a 

 certain degree of uniformity in size, and are within a 

 certain range of size." 



On June 20 last I visited Studland Bay for the purpose 

 of carrying out some new experiments. I found that the 

 musical patch emitted tones louder and more pronounced 

 than 1 had ever heard them there before. The best 

 results were obtained by drawing a thick deal rod, on to 

 the end of which I had fixed a resonator, over the surface 

 of the sand ; sounds produced in this way were heard 

 unmistakably for a considerable distance. The patch 

 averaged 7^ yards in width, and ran parallel with the 

 trend of the shore for some hundreds of yards. The 

 sand on the sea side of the patch was fine, and emitted 

 notes of a high pitch ; that on the land side was coarse, 

 and emitted notes of a lower pitch. The rod drawn 

 across the patch gave, therefore, a great variety of 

 pitch. Many other interesting facts cannot now be 

 referred to, but it is important to state that some of 

 this sand, when taken off the patch, and struck in a 

 box, gave out notes as it did in situ. On trying this 

 sand subsequently at home, the coarse emitted distinct 



' Read before the Bournemouth Society of Natural Science. 



