;66 



SCIENTIFIC NEWS. 



[Nov. 30, 1888. 



cient proof of the excessive minuteness of these ulti- 

 mate molecules or atoms of matter. If one took a piece 

 of musk and put it into a room it would scent a large 

 room for year after year, and every person who went 

 into the room would smell the musk, because minute 

 portions were separated and had come into contact with 

 the membrane of the nose. Yet if one weighed the 

 musk it would not be found that it had lost appre- 

 ciably in weight. They could imagine how excessively 

 minute must be the particles which, though being 

 constantly separated, did not diminish the weight. 

 Those minute particles of gold coloured liquid uniformly; 

 they could not be discovered by the aid of a micro- 

 scope, and they could thus form some idea of how minute 

 those ultimate atoms and molecules of matter must be. 

 Now,those molecules and atoms being so small they, could 

 not study their positions and relations to one another, 

 and the way in which they were built to form such a 

 substance as colloidal silica on the one hand, or crystalline 

 silica on the other, by the aid of the microscope or by 

 any direct means ; but there were means by which 

 they could determine the way in which those ultimate 

 molecules of matter were built up to make those sub- 

 stances, and he would endeavour to illustrate how it was 

 done. Light comes to us through the undulations or 

 waves produced in the ether which surrounds us every- 

 where. These minute waves, or pulsations, in the ether 

 gave rise to the phenomenon known as light, and 

 are of excessively small dimensions. The waves 

 that produced sound or that they saw in liquid were all 

 gigantic as compared with the waves and undulations in 

 the ether. By allowing light to pass through the 

 various substances, and studying the effects produced, 

 they were able to tell how those particles were 

 arranged. 



By means of the lantern the lecturer then proceeded 

 to show how light was used for making out the internal 

 structure of solid bodies (polarisation of light). The 

 reason why those colours were reproduced was that the 

 molecules were built up in a certain fashion. Here they 

 had the means of finding out the way of the building up 

 of the molecules in the substance, and when pieces of 

 quartz were examined in that way they were often found 

 to have an exceedingly complicated structure. If they 

 found opal, or colloid silica, occurring naturally, they 

 never noticed in it any tendency to exhibit definite 

 outward forms. The mass broke out into irre- 

 gular fragments, without any tendency to form defi- 

 nite shapes ; but when they found the other kinds of 

 silica Ihey constantly saw in it a tendency to take on 

 those wonderful forms which belonged to what were 

 called crystals. In virtue of the wonderful inward mole- 

 cular structure they got produced an outward form. Crys- 

 tal forms are, indeed, the outward and visible sign of the 

 inward molecular structure which existed in quartz, and 

 distinguished it from colloidal silica ; and it was wonder- 

 ful how completely its outward form did betray the 

 inward structure. There were a great many internal 

 structures in different kinds of quartz, giving rise to most 

 wonderful appearances when examined by polarised light. 

 When these different varieties of quartz were forming 

 crystals they found the crystals possessed certain 

 peculiarities, a little extra face or other abnormal 

 character, that betrayed at once to the practised eye 

 the fact that the quartz had its peculiar molecular 

 structure ; so that this tendency to take on the outward 

 form of a crystal was connected with its wonderful molecu- 



lar structure, which was betrayed by the substance unc 

 polarised light. But the substance be had been referri 

 to was not the only form of crystalline silica. The 

 were others. One was known as tridymite, and th< 

 were other substances which were crystalline, all 

 which differed in their properties. So they could : 

 what a wonderfully complicated substance the crystalli 

 forms of silica were. In conclusion, he must refer 

 some physical properties which flint presented in a ve 

 marked manner. As he pointed out in his first lectu 

 the character which distinguished flint above all otl 

 things was its hardness. The hardness of flint was r 

 quite so great as that of quartz, but it was somewr 

 greater than that of opal. If a piece of flint was stru 

 against another piece of flint or against a piece of steel 

 spark was produced. A minute portion of the flint or s* t 

 was separated ; the violent blow produced heat suffice 

 to cause this particle to become red-hot. Now, the hai 

 ness of flint was combined with another property, whi 

 gave rise to the uses to which flint had been apphi 

 in the past. It was not only hard, but it was to a certa 

 extent tough ; therefore flint could be used as a cuttin 

 tool in a way that glass could not be used. But the mo 

 striking point about flint was its fracture — the way 

 which it broke. Different substances broke in ve: 

 different ways. Some crystalline substances broke vei 

 easily in some directions, and they got what was call* 

 cleavage. Quartz would not break in a particular mannc 

 If one threw a pebble at a plate-glass windo 

 the result would probably be that on the other sit 

 of the plate-glass a little conical piece of gla 

 would drop out, and with a larger piece of gla: 

 struck suddenly he might get a cone, the ang 

 of the cone being about no degrees. Sometimes a suf 

 ciently violent blow might result in the forms of tv 

 cones, one having sides at an angle of no degrees, an 

 the other the sides at an angle of 30 degrees. Occasional 

 if a blow was struck obliquely he might get a cone lyi 1 

 in an inclined position. This was a very peculiar p"< 

 perty of flint. If a considerable mass of flint was strut 

 they might get the tendency of the forms of a con. 

 giving rise to the appearance exhibited by the outside < 

 a shell, and that fracture was known as a conchoid: 

 fracture. Sometimes if a light tap was given on tt 

 surface of the flint, instead of getting a single cone, thei 

 was around it an inverted cone, producing a cup so ths 

 it looked like a little cone and crater, such as one saw i 

 volcanic countries. The conchoidal structure of flint ws 

 a very remarkable one, and it was this property con 

 bined with hardness and toughness which enabled thei 

 to use it in various ways. If flint was struck with 

 hammer a flake was obtained (specimen exhibited). 1 

 was the fact of the flint having that peculiar fractur 

 which had enabled it to be employed for purposes whic 

 he would have to describe in a future lecture. He hope 

 in the next lecture to show how the microscope enable 

 them to learn more about the internal structure of flin_ 

 and its relation to those two substances which they had 

 been considering that evening — colloidal and crystalline 

 silica. 



Insularity. — Says the Rev. H. H. Slater {Midlan, 

 Naturalist), in a series of articles bearing this title, " I) 

 no other country of which I have any experience is th 

 scientific worker treated by the Legislature with sucl 

 contemptuous indifference as in this." 



