November 14, 1901] 



NA TURE 



In seeking a diluent, one turns naturally first to metallic 

 carbides other than calcium, with the idea of finding a com- 

 mercially possible carbide which will give methane or hydrogen 

 on decomposition with water and could be blended with calcium 

 carbide by the manufactu'rer to suit, if necessary, various require- 

 ments, when we should once more see the early attempts to 

 use for lighting the ordinary household Bray burner repeated 

 with success. Manganese carbide is stated to be easily formed, 

 and by Moissan to be decomposed by water yielding equal 

 volumes of methane and hydrogen, hausmanite (presumably 

 prepared by heating pyrolusite) being recommended. An 

 attempt on my part to make a few grams, though it is true that 

 the amperes at disposal only just reached double figures, failed 

 as regards any gas produced, although reduction undoubtedly 

 took place. I should not presume to quote so insignificant an 

 experiment had not the manager of the Acetylene Illuminating 

 Co., who courteously gave me an interview some moijths ago, 

 told me that the Company's e.speriments on this carbide (and 

 science is indebted to the Company for a great many researches, 

 which I hope it may see fit to publish) had not led to the pro- 

 duction of a carbide at all easily decomposed by water. I 

 suggested the use of manganese mud as being easily obtain- 

 able, very free from silica as compared with pyrolusite, not 

 so highly o-xidised, and in a very fine state of division, and 

 I hope that the Company may see fit to try it. Among other 

 carbides, that of aluminium seems to offer attractions for com- 

 mercial investigation, and although magnesium carbide cannot 

 be prepared in the electric furnace alone, I do not think that 

 dolomite as a substitute for pure carbonate of lime has been 

 ■experimented upon. 



Failing a suitable carbide for dilution, will not some organic 

 chemist come forward with a bye- or waste product which will 

 decompose in the presence of hot caustic lime produced in the 

 generator, with, if not the production of methane, hydrogen or 

 carbon monoxide, at least some indifferent gas, such as nitrogen 

 or carbon dioxide ? 



Investigations are wanted as to the amount of diluent required 

 to banish luminosity under some standard conditions. I can 

 ■only speak at present of carbon dioxide ; a Bunsen burner con- 

 suming one cubic foot of acetylene per hour under six inches 

 water pressure, showing a fully developed luminous zone rather 

 greater in diameter than the sum of the widths of the non- 

 luminous zone on either side, requires a supply of carbon 

 dioxide at the rate of o'l5 cubic feet per hour to destroy 

 completely this luminosity. A. E. MliNBY. 



Felsted, November i. 



Magnetic Iron Ore as a Material for Concrete Blocks. 



The account of harbour works in Nature of October 24 

 (p. 639) causes me once more to draw attention to the great 

 advantage which would be gained by the use of magnetic iron 

 ore as a material for concrete blocks. If magnetite is used 

 instead of ordinary rock in the shape of fragments, and magnetic 

 sand or ilmenite sand instead of common sea sand, concrete 

 blocks can be obtained which have all the strength of the 

 ordinary concrete blocks and which weigh, when immersed in 

 water, exactly twice as much as the ordinary blocks. Such an 

 increase in weight makes the magnetic blocks far superior as 

 regards resistance to the waves. Work constructed with mag- 

 netic blocks will stand when other work will be destroyed. 

 This superior effect of magnetic blocks is quite independent of 

 the size of the blocks. The artifici d increase of the size of 

 ordinary concrete blocks is mentioned as a means of increasing 

 the power of resistance, but there arei certain to be some objec- 

 tions to this method, and if the great masses are ruptured after 

 the rusting away of the cases, portions may give way. It is 

 therefore better and more convenient to use the superior com- 

 position. As regards the expense, it may be mentioned that to 

 obtain a good effect it is only necessary to use magnetic blocks 

 for the most exposed spots of a dam, and more in the nature of 

 a surface coating. There are immense natural deposits of 

 magnetite, also of titanium ore, which latter is not of 

 value for steel making, and it would surely be possible to obtain 

 the necessary quantities in Scandinavia, or if for harbours in 

 the East, then there would be inexhaustible supplies in southern 

 India not too far from the coast. It has been argued that the 

 iron ore would decay on exposure to sea water and that it 

 would injure the cement. This may be true for inferior iron 

 ■ores, but not for rich, pure magnetite and ilmenite, as I have 



NO. 1672, VOL. 65J 



proved by direct experiments. I have exposed fragments of 

 magnetite to the action of filtered sea water in clean glass jars 

 where every trace of decomposition would have been detected, 

 but though I continued the test for a year the specimens stood 

 the test very well. Moreover, I made sample blocks with 

 Portland cement and subjected them to crushing tests, which 

 showed them to be perfectly satisfactory as regards strength. 



H. Warth. 



The San Clemente Island Goat. 



L.\ST summer, at San Pedro, California, I was shown a 

 goat which had just been brought over from San Clemente 

 island. Mr. Miiller, the owner of the animal, told me that the 

 goats of that island, running practically wild since the unknown 

 date of their introduction, were all alike, constituting an easily 

 recognisable race. The animal was quite reddish, about the 

 colour of a red deer ; front of face black; a pale (reddish) stripe 

 down each side of nose, and enclosing the eye ; cheeks black ; 

 chin light; ears blackish above; neck and anterior part of body 

 strongly suffused with black. The light facial stripes were par- 

 ticularly distinct. 



The Santa Catalina Island goats, I was informed, are variously 

 coloured. This is doubtless due to the fact that Catalina is a 

 popular resort, and fresh animals are frequently introduced. 



T. D. A. COCKERELL. 



East Las Vegas, New Me.xico, U.S.A., October 27. 



Food of Grass Snakes. 



May I say, in defence of Dr. Gerald Leighton (see p. 625), 

 that on two occasions I have found mice inside grass snakes. 

 The first case was on a moor near Parkstone, Dorset, where on 

 opening a smallish snake we found a mouse only partly digested. 

 The other case occurred here last year, when I found a small 

 shrew in a large grass snake. Also with regard to them 

 swallowing birds, I have three times found birds inside them. 

 In each case they were young ones ; two were probably young 

 larks (they were both in one snake), and the other was a young 

 robin. C. M. Rogers. 



Wellington College, Berks, October 2S. 



THE OBSERVATORY OF MONT BLANC} 



IN observing the physical features of the Alpine 

 regions, M. Vallot and the several members of his 

 family show a devotion that no discouraging circum- 

 stances can damp, and an energy that rises superior to 

 the inclemencies of the weather and the loneliness of the 

 situation. His original observatory, constructed after 

 much labour and in spite of many difficulties, was found 

 to be in an unfortunate position, owing to the accumula- 

 tion of snow with which neither labour nor expense 

 could efficiently deal. Without hesitation this construc- 

 tion is abandoned, and in the light of greater experience 

 a fresh site is selected and a new observatory built, 

 where, from the peculiarity of configuration, snow cannot 

 collect and interfere with the progress of the work. 

 This building, constructed in 1898, admirably fulfils its 

 purpose, and here, at an altitude of 4358 m., among the 

 eternal snows, M. Vallot and his band of energetic 

 labourers pursue their scientific avocations. These are 

 sufficiently various, and in the present volumes we have 

 the result of three distinct investigations, one dealing 

 with the influence of barometric pressure on the chemical 

 action of solar light, another on the velocity of water in 

 streams and under glaciers, while the last gives an 

 account of experiments undertaken with the view of 

 detecting the rate and character of glacier motion. 



Of the first of these discussions it is sufficient to say 

 that the author aims at a re-examination of the adequacy 

 of the formula found by Bunsen and Roscoe in similar 

 researches, wherein occurs a numerical coefficient 



1 " Annales de I'Observatoire mct^oroiogique physique et glaciaire du 

 Mont Blanc." Pubises sous la direction de J. Vallot, Fondateur et 

 Directeur de TObservatoire. Tome iv. Pp. ix -f- iSq. Tome v. Planches 

 du Tome iv. (Paris : G. Steinheil, Editeur, 190D.) 



