'ov. 30, 1888.] 



SCIENTIFIC NEWS. 



563 



r .t showed that the physical characters of Chesil 

 ;. ch, except for size and composition of its 

 rticles, are identical with those of a singing 

 > ach ; and he thinks the rubbing together of 

 ; rounded particles of sand may be the cause of 

 t sound emitted by musical sand. Mr. Carus-Wilson 

 tailed experiments he had made in the course of his 

 /estigations. He had endeavoured to make a musical 

 »^ by sifting ordinary sand through muslin of various 

 jrees of fineness, and afterwards treating it with acids, 

 this means he had obtained a sand composed of clean 

 lins of uniform size, but which was not musical. The 

 tins, however, were angular, and not rounded. It 

 uld appear there must be considerable difficulty in 

 aining a successful result to such an experiment, as 

 : musical properties of sand depend on most delicate 

 iditions. The mere handling of such a sand is 

 jugh to make it mute, or if brought home and damped 

 :h water it is made for ever mute, which is very 

 •ious, as the same sand, exposed on its beach, is con- 

 ntly exposed to the action of sea or rain water, and 

 when dry is again musical. The Studland Bay sand 

 nusical only on its own beach. Mr. Carus-Wilson has 

 'Ught away many samples from that locality, but has 

 ,'er been able to bring with it its musical note. The 

 id from the Isle of Eigg, first described by Hugh 

 Her, appears to be one of the best and most famous of 

 se musical sands. Of this the lecturer had a sample, 

 ich, on percussion with the wood handle of a seal, 

 itted a loud shrill sound. This sand is the result of 

 disintegration of the rocks in that locality, and has, 

 ough long periods of time, been subject to a separating 

 ion by wind and wave. The result is, the coarser 

 inded particles are left high, and constitute the sing- 

 beach ; the finer are carried away to another part of 

 bay, where they are found. In much the same way the 

 ging beach in Studland Bay has been formed by the 

 ion of the prevailing wind separating and carrying 

 ay the finer particles of sand, leaving the larger ones, 

 inding and polishing them by attrition. The delicate 

 iditions necessary for the formation of a singing beach 

 : well shown here, where it is a rather long interrupted 

 ip not more fifteen yards wide. 



\n interesting discussion followed, in which the 

 jsident, and Messrs. Dolamore and Curtis took part. 



FLINTS. 



'HE second of a series of lectures on Flints was given 

 on Monday evening of last week in the theatre of 

 : School of Mines, by Professor J. W. Judd, F.R.S. 

 e lecturer commenced by saying that at their last 

 :eting he endeavoured to point out how, by a series 

 analyses, the chemist arrived at the conclusion 

 .t quartz consisted of silica, and nothing but silica. He 

 :n proceeded to point out that the substance silica, or 

 xide of silicon, consisted of two chemical elements — 

 : gas known as oxygen, and the solid substance known 

 silicon. He remarked upon the great interest which 

 ached to those two elements — oxygen and silicon 

 arising from the fact that oxygen constitutes one-half 

 the crust of the globe, while silicon constitutes nearly 

 quarter, thosp two elements by themselves making 

 , therefore, three-fourths of the earth's crust. He 

 ;n proceeded to point out the wonderful analogy there 

 is between the element silicon and the element carbon. 

 : showed that while carbon formed the basis of the 



organic world, silicon constituted the basis of the mineral 

 or inorganic world. He showed further that those two 

 substances — carbon and silicon — presented some remark- 

 able analogies one with the other. Those two substances 

 were each capable of existing in a number of different 

 conditions known as allotropic forms of the substance. 

 The diamond was one form of carbon ; carbon was some- 

 times found as a black substance — charcoal — and 

 sometimes crystallised as graphite ; sometimes, again, it 

 is found in meteorites, which come to us through space 

 in the form called Cliftonite. He showed there were 

 three forms of silicon, analogous to the diamond, Cliftonite, 

 and charcoal. Proceeding from the condition of the 

 element silicon to the compound substance silica, he 

 pointed out that silica was the most abundant of the binary 

 compounds in the earth's crust — that it constitutes, either 

 alone or in combination with other substances, no less 

 than two-thirds of the earth's crust. He had then pro- 

 ceeded to point out that silica, like silicon — they must 

 keep clearly in mind the distinction between the com- 

 pound of silica and the element silicon — and carbon 

 could exist in other states, and he had also briefly indi- 

 cated, in concluding his lecture, that that difference 

 between substances having the same ultimate chemical 

 composition was principally due to the way in which 

 their atoms or molecules were arranged in building up 

 the substance, so that if the arrangement of atoms or 

 molecules be altered without changing the chemical com- 

 position, of the substance they might completely alter 

 its properties. Now there were two forms of silica which 

 were especially worthy of their attention. There were 

 other forms of silica, as he should point out presently, 

 but there were two forms which in their study of flints 

 they must especially bear in mind — the substance known 

 as colloidal silica, a kind of gluey, jelly-like substance ; and 

 the crystalline, or ice-like form of silica. Now, colloidal 

 silica and crystalline silica have identically the same 

 chemical composition, but in a great number of points 

 they differ remarkably in their physical and other pro- 

 perties. First of all he would refer for a moment to the 

 differences of their chemical behaviour under different 

 conditions. If he were to put a piece of crystalline 

 silica into a vessel of water he might leave it there prac- 

 tically for an indefinite time, and it would undergo no 

 change. There would be no tendency for the substance 

 to dissolve, and as he pointed out last time, he could not 

 dissolve it directly in any substance except in the power- 

 ful acid known as hydrofluoric acid. But colloidal silica 

 might easily be made to pass into solution. He would 

 call their attention to the case of minerals in the gallery 

 above the theatre, where they would see water contain- 

 ing a considerable quantity of colloidal silica in solution. It 

 appeared perfectly bright and clear ; and they could not 

 tell it from pure water. Now, there was another chemical 

 difference between crystalline silica and colloidal silica 

 besides the tendency of the one to pass into a solution 

 and the other to resist solution. Quartz showed no ten- 

 dency to combine with water, but colloidal silica did very 

 easily combine with water. It was true that by raising 

 the temperature to a certain extent some of the water 

 separates from colloidal silica,but it is very difficult indeed 

 to separate the whole of the water from that substance. 

 Chemists had found out that there are very definite com- 

 pounds of this silica, or dioxide of silicon, with water — one 

 known as silicic acid, and others containing larger pro- 

 portions of water. 



Now, besides that difference of chemical behaviour, 



