358 



NA TURE 



[August 9, 1883 



of about 15J lbs. of powder a ball of 66 lbs., and made of 

 cast-iron, a treacherous material for such purposes. We have 

 now guns built up on well understood mechanical principles, of 

 the most trustworthy and suitable material known, weighing 100 

 tons and firing with charges of 772 lbs. of powder shells of 

 2000 lbs. Already considerable experience has been obtained 

 with guns of this weight. No fewer than fourteen have been 

 issued from the Elswick Works, and several more are in the 

 course of construction. 



" Perhaps the most interesting feature in these formidable 

 pieces of ordnance is the ease, rapidity, and noiselessness wilh 

 which they are worked. It is of course impossible that such 

 ponderous pieces could be brought into practical use without the 

 aid of some mechanical appliances ; but it is scarcely an exaggera- 

 tion to say that nolhing can work with greater precision and 

 ease and be better under control than the hydraulic machinery 

 employed for opening and closing the breech of the gun, ram- 

 ming home the charge, elevating or depressing, running in or 

 out, and training with accuracy on a given object. Two men 

 working levers perform all these operations, and they, together 

 with the machinery, are under complete protection from an 

 enemy's fire. 



"The projectile when fired has an energy imparted to it equal 

 to nearly 48,450 foot tons, yet the gun is under such entire con- 

 trol that its recoil, due to this enormous force, is completely 

 absorbed in a distance little exceeding three feet, without undue 

 strain to any part of the mechanism. When it is remembered 

 that the internal dimensions of the costly turrets in which guns 

 of this size are ordinarily mounted depend mainly upon the 

 space allowed for recoil, it is clear that it is of very great impor- 

 tance to reduce this space to a minimum. 



" The fact which lies at the basis of these results is of course 

 this, that the attainment of a high speed requires a more perfect 

 machine, and with a more perfect machine more perfect work is 

 turned out. 



" In conclusion, it should be remembered that high speed, espe- 

 cially the speed of rotation, is almost necessary to give perfect 

 accuracy and steadiness to motion, as in the case of an ordinary 

 spinning top, of a gyroscope, and again of the ingenious centri- 

 fugal machines now in use for separating cream, &c. The speeds 

 which we find id Nature are beyond all conception high, and her 

 operations under those speeds are absolutely true and perfect. 

 We cannot hope to vie with Nature even to an infinitesimal 

 fraction of her powers of speed and accuracy ; but in this, as 

 in many other great lessons taught by her, we see the direction 

 in which we must travel in our efforts towards the perfection of 

 work. 



"Finally, it is unfortunately a necessity that nations should 

 still provide themselves with materials for war ; and engineers 

 have to devote their minds to the perfecting of such materials. 

 It does not seem impossible that projectiles may be gradually 

 developed, of such precision and devastating power as to make 

 the existence of life witbin a certain range well nigh impossible. 

 Were this accomplished, it is clear that nations would hesitate 

 more and more before rushing into a war so destructive ; and 

 even if they did so, its rapid termination would unquestionably 

 go far to diminish the various miseries which war always brings 

 in its train. Hence it may not unfairly be said that the attention 

 and skill given to the arts of war is really our best warrant for 

 the continuance of peace." 



On the next morning the papers read were on the " History of 

 ihe Coal and Iron Industries in the Liege District," by M. 

 Edouard de Laveleye, and on the "Manufacture of Zinc in 

 Belgium," by M. St. Paul de Sincay. The first of these was 

 generally of an historical character, giving many interestingdetails 

 as to the development of collieries and ironworks in Belgium. 

 A claim was put in on behalf of Belgium for two most important 

 discoveries in the metallurgy of iron, namely, the blast furnace 

 and the cementation process. With regard to the present posi- 

 tion of coal-working in this district, it was observed that all the 

 difficulties which generally beset the mining of coal have to be 

 encountered in their severest form. The chief of them — fire- 

 damp — is nowhere so destructive, though its effects have been to 

 a great extent obviated by the introduction of the Davy lamp 

 and afterwards the improved safety-lamp of Mueseler. This 

 lamp will resi-t a current of air of 15 feet per second, and has 

 also the great property of self-extinguishment. In the recent 

 disaster at L'Agrappe, which cost the lives of more than loo 

 miners, a sudden escape of gas issued from the shaft and burnt 

 for several hours like an enormous gas-burner ; but there was no 



explosion inside the mine, the 220 Mueseler lamps which were 

 underground at the time having all been extinguished. Similar 

 escapes of gas have taken place on other occasions and in enor- 

 mous volume, without having previously given any indication of 

 their appearance. Science appears to be powerless to prevent 

 these disasters. 



The second paper gave a sketch of the manufacture of zinc, 

 which is a special trade in Belgium. Little was said as to 

 the details of metallurgy, but it appears that the Belgian 

 process, invented by Dony, of Liege, in 1S10, is superseding all 

 others, even in England. The difficulty and loss in reduction 

 are, h >\\ ever, very great, and the labour is described as harder 

 even than that of the puddler. 



The third paper, by M. Melin, was on "The Manufacture of 

 Sugar from Beetroot," and formed a complete and exhaustive 

 monograph on a manufacture of which but little is known in 

 England. We regret that we can only give the briefest possible 

 sketch of the processes. The beetroot, of which the cultivation 

 was fully described, contains about 95 per cent, of juice in weight, 

 and 5 per cent, of cellulose. These 95 parts of juice contain 

 10 parts of sugar, 2 of solid matter, and 83 of water. In manu- 

 facturing, the special point to be considered is the percentage of 

 sugar, together with the purity of the juice. The manufacture is 

 carried on in the winter only, and the beetroots are piled in silos 

 until they are required for use. They are then washed, and 

 are now ready for the extraction of the juice. For this pur- 

 pose two systems are employed. On the first or hydraulic 

 system, the roots are immersed in powerful rasping machines, 

 and so reduced to pulp. This pulp is collected in sacks, which 

 are piled up one upon the other between the table and the pres- 

 sure head of a hydraulic press. The press is started, and acts 

 with a pressure of about 450 lbs. per square inch on the pile of 

 sacks, squeezing the juice through them. The dry pulp is used 

 for feeding cattle, and is of considerable value. On the second 

 or diffusion system the beetroots are cut up by a cutting machine 

 into small slices called cassettes. These are placed in cylindrical 

 vessels with an opening at the top for charging, and another at 

 the bottom for emptying. The*e vessels are filled with water, 

 and the result is that a current of endosmosis takes place from 

 the water towards the juice in the cells, and a current of exos- 

 mosis from the juice towards the water. These currents go on 

 until equilibrium is produced ; and if fresh water is substituted 

 they begin afresh. In this way the whole of the sugar contained 

 in the cells is gradually drawn out. On the other hand, the 

 water passes from the more exhausted to the less exhausted cells, 

 and thus gradually increases in richness. A number of such 

 vessels are used, forming what is called a diffusion battery ; but 

 in each of them the process going on is the enriching of the juice 

 on the one hand and the impoverishing of the slices on the 

 other. The slices are finally pressed in order to remove the 

 residue of juice, but this is never effected so completely as by 

 the hydraulic method. 



The next process is that of defecation, which consists in 

 adding milk of lime to the juice, in order to neutralise the 

 organic acids which are precipitated, and also to decompose the 

 salts of potassium, sodium, and ammonia. The result is that the 

 dark brown juice becomes perfectly clear and of an amber 

 colour. The scum which floats on the top, and which contains 

 much juice, is passed through filtering presses, and the dried 

 cake is sold as manure. After defecation the juice is filtered, 

 twice at least, through animal charcoal under a sufficient 

 pressure. It is then evaporated and transformed into syrup in a 

 series of three vertical vessels, of which the first communicates 

 with the second, the second with the third, and the third with a 

 condenser. Steam is admitted to the first, and passes through 

 to the last ; and, owing to the partial vacuum produced by 

 means of the condenser, causes an evaporation of the juice in 

 all three. The next process is that of boiling this group, so as ti 1 

 allow the sugar to crystallise. This goes on within cast-iron 

 vessels under a high vacuum, and heated by steam at high 

 pressure circulating through worms. After a certain amount of 

 evaporation, crystallisation begins in the form of an immense 

 number of small grains of sugar. To develop these grains syrup 

 is pumped in at regular intervals and with great care, so that the 

 crystals may grow steadily and may be large, regular, and hard. 

 Finally the crystals are dried by ceasing to supply syrup and 

 introducing a current of steam. After eight to ten hours the 

 sugar is removed from the boilers, and placed in vertical turbines 

 running at iooo revolutions per minute. Under the action of 

 centrifugal force the boiled mass is spread upon the outsides of 



