58 



NATURE 



{_Nov. 15, 1883 



were developed, it is difficult to say how, in the forge or 

 furnace itself, and amid the smoke and din of practical 

 work. At the same time the experiments of Bessemer 

 were for the most part carried out with a distinct eye to 

 their future application in practice, and their value for 

 our present purpose is therefore not so great. The same 

 we believe may be said with regard to the great rival of 

 the Bessemer converter, viz. the Siemens open hearth ; 

 although this forms in itself a beautiful application of the 

 scientitic doctrine that steel stands midway, as regards its 

 proportion of carbon, between wrought iron and pig iron, 

 and ought therefore to be obtainable by a judicious 

 mixture of the two. The basic process is the latest 

 development, in this direction, of science as applied to 

 metallurgy. Here, by simply giving a different chemical 

 constitution to the clay lining of the converter, it is found 

 possible to eliminate phosphorus — an element which has 

 successfully withstood the attack of the Bessemer system. 

 Now, to quote the words of a German eulogiser of the 

 new method, phosphorus has been turned from an enemy 

 into a friend ; and the richer a given ore is in that sub- 

 stance, the more readily and cheaply does it seem likely 

 to be converted into steel. 



These latter examples have been taken from the art of 

 metallurgy ; and it may of course be said that, considering 

 the intimate relations between that art and the science of 

 chemistry, there can be no wonder if the former is largely 

 dependent for its progress on the latter. I will there- 

 fore turn to what may appear the most concrete, prac- 

 tical, and unscientific of all arts — that, namely, of the 

 mechanical engineer ; and we shall find that even here 

 e.xamples will not fail us of the boons which pure science 

 his conferred upon the art of construction, nor even 

 perhaps of the reciprocal advantages which she has de- 

 rived from the connection. 



The address of Mr. Westmacott, from which I have 

 already taken my text, supplies in itself more than one 

 instance of the kind we seek — instances emphasised by 

 papers read at the meeting where the address was spoken. 

 Let us take, first, the manufacture of sugar from beetroot. 

 This manufacture was forced into prominence in the early 

 years of this century, when the Continental blockade 

 maintained by England against Napoleon prevented all 

 importation of sugar from .America ; and it has now at- 

 tained very large dimensions, as all frequenters of the 

 Continent must be aware. The process, as exhaustively 

 described by a Belgian engineer, M. Miflin, offers seve- 

 ral instances of the application of chemical and physical 

 science to practical purposes. Thus, the first operation 

 in making sugar from beetroot is to separate the juice 

 from the flesh, the former being as much as 95 per cent. 

 of the whole weight. Formerly this was accomplished 

 by rasping the roots into a pulp, and then pressing the 

 pulp in powerful hydraulic presses; in other words, by 

 purely mechanical means. This process is now to a large 

 extent superseded by what is called the diffusion pro- 

 cess, depending on the well known physical phenomena 

 of eiidosmosis and exosiiiosis. The beetroot is cut up 

 into small slices called " cossettes," and these are placed 

 in vessels filled with water. The result is that a current 

 of endosmosis takes place from the water towards the 

 juice in the cells, and a current of exosmosis from the juice 

 towards the water. These currents go on cell by cell, 

 and continue until a state of equilibrium is attained. The 

 richer the water and the poorer the juice, the sooner does 

 this equilibrium take place. Consequently the vessels 

 are arranged in a series, forming what is called a diffu- 

 sion battery ; the pure water is admitted to the first 

 vessel, in which the slices have already been nearly 

 exhausted, and subtracts from them what juice there is left. 

 It then passes as a thin juice to the next vessel, in which 

 the slices are richer, and the process begins again. In 

 the last vessel the water which has already done its 

 work in all the previous vessels comes into contact with 



fresh slices, and begins the operation upon them. The 

 same process has been applied at the other end of the 

 manufacture of sugar. After the juice has been purified, 

 and all the crystallisable sugar has been separated from 

 it by boiling, there is left a mass of molasses, con- 

 taining so much of the salts of potassium and sodium 

 that no further crystallisation of the yet remaining sugar 

 is possible. The object of the process called osmosis is to 

 carry off these salts. The apparatus used, or osmogene, 

 consists of a series of trays filled alternately with molasses 

 and water, the bottoms being formed of parchment paper. 

 A current passes through this paper in each direction, 

 part of the water entering the molasses, and part of the 

 salts, together with a certain ciuantity of sugar, entering 

 the water. The result of thus freeing the molasses from 

 the salts is that a large part of the remaining sugar can 

 now be extracted by crystallisation. 



Another instance in point comes from a paper dealing 

 with the question of the construction of long tunnels. In 

 England this has been chiefly discussed of late in connec- 

 tion with the Channel Tunnel, where, however, the con- 

 ditions are comparatively simple. It is of still greater im- 

 portance abroad. Two tunnels have already been pierced 

 through the Alps ; a third is nearly coinpleted ; and a 

 fourth, the Simplon Tunnel, which will be the longest of 

 any, is at this moment the subject of a most active study 

 on the part of French engineers. In Ainerica, especially 

 in connection with the deep mines of the western States, 

 the problem is also of the highest importance. But the 

 driving of such tunnels would be financially if not physi- 

 cally impossible, but for the resources which science has 

 placed in our hands, first, by the preparation of new 

 explosives, and, secondly, by methods of dealing with the 

 very high temperatures which have to be encountered. 

 As regards the. first, the history of explosives is scarcely 

 anything else than a record of the application of chemical 

 principles to practical purposes — a record which in great 

 part has yet to be written, and on which we cannot here 

 dwell. It is certain, however, that but for the invention 

 of nitroglycerine, a purely chemical compound, and its 

 development in various forms, more or less safe and con- 

 venient, these long tunnels would never have been con- 

 structed. As regards the second point, the question of 

 temperature is really the most formidable with which the 

 tunnel engineer has to contend. In the St. Gothard 

 Tunnel, just before the meeting of the two headings in 

 February, 18S0, the temperature rose as high as 93° Fahr. 

 This, combined with the foulness of the air, produced 

 an immense diminution in the work done per person and 

 per horse employed, whilst several men were actually 

 killed by the dynamite gases, and others suffered from a 

 disease which was traced to a hitherto unknown species 

 of internal worm. If the .Simplon Tunnel should be con- 

 structed, yet higher temperatures may probably have to 

 be dealt with. Although science can hardly be said to 

 have completely inastered these difficulties, much has 

 been done in that direction. A great deal of mechanical 

 work has of course to be carried on at the face or far 

 end of such a heading, and there are various means 

 by which it might be done. But by far the most satis- 

 factory solution, in most cases at least, is obtained by 

 taking advantage of the properties of compressed air. Air 

 can be compressed at the end of the tunnel either by steam- 

 engines, or, still better, by turbines where water power 

 is available. This compressed air may easily be led in 

 pipes to the face of the heading, and used there to drive 

 the small engines which woik the rock-drilling machines, 

 &c. The eiSciency of such machines is doubtless low, 

 chiefly owing to the physical fact that the air is heated 

 by compression, and that much of this heat is lost whilst 

 it traverses the long line of pipes leading to the scene of 

 action. But here we have a great advantage from the 

 point of view of ventilation ; for as the air gained heat 

 while being compressed, so it loses heat while expand- 



