388 



KNOWLEDGE & SCIENTIFIC NEWS. 



[March, igo6. 



Herr Pahisch. The\' are all resinous bodies, free from nitrogen, 

 apparently related to one another, and extremely poisonous 

 to iish. The compound isolated from D. ellipHca is termed 

 derriik, and has the formula, C.t, H.io Oio. 



The Distillation of Gold. 



M. Moissan, to whom \vc owe so much of our knowledge of 

 the behaviour of chemical elements at a high temperature, 

 has found that there is no difficulty in distilling gold in an 

 electric furnace, and that the liquid condenses on a cold sur- 

 face in minute crystals and threads, which behave exactly 

 like ordinary gold in a finely-divided state. The boiling point 

 of gold is higher than that of copper or tin. but lower than that 

 of iime ; so that on distilling alloys of gold with copper or tin a 

 fractional separation is effected, the gold being the last to pass 

 over. When an alloy of gold and tin is distilled with lime, 

 the distillate, consisting of a mixture of gold, oxide of tin, and 

 lime, has the beautiful colour and other characteristics of the 

 well-known Purple of Cassiiis used for colouring glass and 

 porcelain. Hitherto this substance has only been produced 

 by wet methods, such as treating a solution of gold in aqua 

 rcgia with solutions of the chlorides of tin, and the new dry 

 method of preparing it may be found of commercial import- 

 ance. Deposits of other shades of colour can be obtained by 

 mixing the alloy with silica, magnesia, alumina, or other 

 oxides, in place of lime, before the distillation. 



Flour Dust Explosions. 



Fine, dry, organic dust, such as that of coal, flour, soot, or 

 cotton, w'ill take fire with explosive violence, and man)' 

 terrible accidents have occurred in mines and mills through 

 ignorance of this fact. After the explosion in the Haswell 

 Collieries in 1S44, the subject was investigated by Faraday 

 and Lyell, who made recommendations as to better ventila- 

 tion of the mines ; but no precautions appear to have been 

 adopted until later accidents led to the appointment of a 

 Royal Commission. In 1S72, a frightful disaster took place 

 in the Tradeston flour mills, near Glasgow, but no one sus- 

 pected the cause until Mr. Watson Smith showed that a 

 mixture of flour dust and air would burn explosively in the 

 same way as coal dust and air. An investigation made in 

 18S1 by Messrs. Rankin and Macadam, brought to light the 

 fact that many unexplained explosions had occurred in other 

 flour mills, notably in Bnda-Pest. These, too. were attributed 

 to the dry flour dust having been ignited by sparks from the 

 stone rollers, and the conclusion was arrived at that "it seems 

 scarcely possible to guard against such accidents." Mr. 

 Watson Smith has reviewed the whole subject in a paper 

 read before the Society of Chemical Industry, and points out 

 that to this day flour mills of the old type are still in use and 

 are inevitably exposed to the same risks as the mills in 18S1, 

 notwithstanding the fact that means of obviating all danger 

 were devised by Mr. Simon, of Manchester. These improve- 

 ments consisted in replacing stone rollers by iron rollers, and 

 in the introduction of what is known as the "Cyclone"' 

 System of collecting the flour dust. The dust-laden air from 

 the rollers is conducted into a conical separator where, by 

 means of the centrifugal action, the dust slides down the side 

 to the bottom, and escapes through a small opening into a 

 receptacle, while the air, freed from dust, is whirled upwards 

 again, and leaves the "cyclone" through a cowl in the roof. 

 In addition to the production of a purer flour, the method has 

 the further advantage of preventing injury to the workpeople, 

 who otherwise inhale the dust. 



GEOLOGICAL. 



Bv Edward A. M.\rtin, F.G.S. 



Glacial Beds of Triassic Age. 



The Dwyka Conglomerate found at the base of the Karroo 

 System in the Transvaal is now better known as the Glacial 

 Conglomerate, since the former differences amongst geo- 

 logists as to the nature of the formation have all but passed 

 awav. At one time it was generally supposed to have been 

 of igneous origin, and great hesitation was naturally felt 

 before accepting the glacial origin of the beds, situated as 

 thev are in a system which is certainly not vounger than the 

 New Red (Triassic). Mr. E. T. Mellor, F.G.S. , has studied 



the district lying east of Pretoria to near Middelburg, and 

 divides the Karroo rocks into an Upper and a Lower division. 

 The former is sometimes known as the " High- Vela Series," 

 and consists of various grits and shales with conglomerates 

 and coal seams, whilst the latter consists of various glacial 

 deposits, including the Dwyka Conglomerate, and associ- 

 ated shales and sandstones. The conglomerate averages 

 about 50 feet thick, and may in depressions reach as much 

 as 200 feet. The constituent boulders and sub-angular rock 

 fr.-igments show no definite arrangement, and lie in a con- 

 fused mass. It is noteworthy that the surface of the older 

 rocks underlying the glacial conglomerate are frequently 

 polished and cle;irly striated, and also that the striae exhibit 

 a remarkable constancy of direction towards the south. 



Neolith fronn South Norwood. 



A portion of a neolithic flint implement has reached me 

 which was found in a garden in .South Norwood, on the 

 slope. of the hill below Grange Park. It bears a marked 

 resemblance to one that was found by a workman in the 

 riiornlon Hrath gravel pits some few years ago, and was 



Neolith from South .NorwooJ. (Natural size.) 



referred lo by Dr. A. E. Salter, F.G.S., in his paper before 

 the Geologists' .Association, entitled " Pebbly Gravels." 

 The portion of an implement now found is well preserved, 

 although on both sides a molecular change has proceeded 

 in the silica, resulting in a banded appearance of the white 

 ])ortion when seen in section below. It is of excellent shape, 

 and well polished. 



Nilotic Geology. 



The somewhat vexed question of the mutuiil relations of 

 the Cretaceous and Eocene systems in the vallev of the Nile 

 has been to some extent determined by some useful ob- 

 servations which have been made by Mr. H. J. L. Beadnell, 

 formerly of the Egyptian Geological .Survev. In the autumn 

 of 1904 he took advantage of certain opportunities which 

 presented themselves to him to examine the desert margins 



