SCIENTIFIC NEV\^S. 



[March 1st, 1 5 



Use of Cold Air for Tunnelling. — One of the most 

 populous parts of Stockholm, that part situated north of the 

 Lake Maelar, is crossed by a ridge of hills reaching in 

 height to seventy feet, and fairly steep. The ordinary steps 

 were thought neither picturesque nor convenient. It was, 

 therefore, decided to drive a tunnel through the ridge. 

 The greater part of this tunnel did not cause any particular 

 difficulties; but near the western end, and just where 

 the tunnel had to pass within a few feet of the founda- 

 tions of two houses of five stories each, sand, with a clay 

 medium, but rather permeable to water, was encountered. 

 The water proving very troublesome, Mr. Lindmark, the 

 engineer-in-chief, thought of refrigerating machines, which 

 have already for several years been advantageously em- 

 ployed in sinking the foundations of bridges. One of 

 Lightfoot's cold-air machines was ordered, supplying over a 

 thousand cubic yards of air per hour, cooled down to 

 twenty-two degrees below zero Fahrenheit. A work- 

 chamber was partitioned off by means of a double wall of 

 wood, the space between the wooden boards being filled 

 with charcoal. When this chamber had been cooled for sixty 

 hours, the ground was found frozen to the depth of five 

 feet ; the sand was also frozen a foot or more ahead, but 

 hardly frozen above. The cold-air machine was kept 

 going afterwards only during the night, when the tempera- 

 ture sank down to four and nine degrees below freezing 

 point. For the masonry a mixture of one part of beton, one 

 part of Portland cement, 2| parts of sand, and six parts ol 

 small granite was used. The work proceeded at the rate 

 of a foot a day for about eighty days ; then a firmer sand 

 was struck, no longer necessitating the use of the re- 

 frigerator. As this refrigerating plant was thus needed for 

 a short period only, it increased the cost of the construction, 

 disproportionately, to a little over ;£,20 per foot. The lineal 

 dimensions of the tunnel are 755 feet in length, 13 feet in 

 height, and about the same in width. Of the two houses 

 referred to one suffered in no way, but the front wall of the 

 other, which cannot be called a well-built house, and was 

 not new, has sunk one inch. 



Galloflavin is a new yellow dye, a German patent of the 

 Badische Anilin und Soda Fabrik, at Ludwigshafen, on the 

 Rhine. It is made out of gallic acid, one of the constituents of 

 gallnuts, in a fairly simple way. The alcoholic solution of gallic 

 acid is mixed with caustic soda or potash, less of the latter 

 being taken than needed for saturation; the liquid becomes 

 olive-green, and is oxidised by means of the oxygen of the air 

 at a low temperature. The colouring matter falls out, is re- 

 dissolved in hot water and decomposed by means of hydrochloric 

 or sulphuric acid, of which up to fifty per cent, may be used. 

 During this operation the liquid is kept boiling until the precipi- 

 tating dye has become crystalline. On being then washed with 

 warm water it needs no further preparation. Applied with a 

 clay mordant the galloflavin imparts to the cotton fibre a greenish 

 yellow tint ; and when passed through tin salt it becomes a pure 

 yellow, which withstands the effect of air, light, and soap, very 

 well. 



Velocity of Ocean Currents. — Admiral Bouquet de la 

 Grye has made an interesting report to the Academie des 

 Sciences, at Paris, on a series of experiments instituted to test 

 the velocity of currents in the north Atlantic, by means of light 

 water-tight casks or vessels launched into the sea at a con- 

 siderable distance from the land. Some such casks, launched 

 off the Azores in 1885, reached the land after an interval of time 

 which indicated a daily rate of motion of from two to four miles. 

 Later observations indicate a quicker rate of movement. Of 

 500 launched in deep sea off Cape Finisterre, 12 arrived at the 

 French coast, a little below Arcachon, after an interval which 

 suggests an average daily rate of travel of about six miles. Some 

 of the vessels were of glass, some of copper. Those of glass, 

 floating on the surface, were exposed more to the buffetings of 

 the waves, as well as to the influence of the currents ; so that it 

 may not be easy to determine how much each of these factors 

 may have contributed to the actual movement. 



THE GAS ENGINE. 



GAS engines have now such a recognised position among 

 motors, that we think a few general particulars may 

 be useful to our readers, and at the same time we take the 

 opportunity of discussing portions of a very useful hand- 

 book on the subject, by Mr. Dugald Clerk, which has 

 recently been published."* 



The Lenoir engine, shown in Fig. i, and patented in 

 i860, was the first to emerge from- the experimental 

 stage, and although several of these engines were made in 

 England and France, their success was not great, owing 

 chiefly to the working expenses being excessively high. A 

 sectional plan of the cylinder of this engine is shown in 

 Fig. 2,t and from this it will be seen that it closely 

 resembles a steam engine, with valves arranged to 





Fig 3 



admit gas and air, and to discharge the products 

 of combustion. The ignition of the charge was effected 

 by an electric spark. The water surrounding the cylinder 

 was intended to prevent the metal being over-heated, 

 but as a matter of fact this was only partially suc- 

 cessful, and the piston often became too hot to work. In 

 1867 IVIessrs. Otto and Langen exhibited the vertical engine 

 shown in Fig. 3, and as its gas consumption per horse-power 

 was only half that of the Lenoir and other engines previously 

 made, it naturally attracted much attention, and a con- 

 siderable number were sold. It was, however, extremely 

 noisy and quite unfit for many uses. In 1876 this engine 

 was entirely superseded by the horizontal Otto engine, now 

 so much used. An example is given in Figs. 4 and 5, p. 13. 

 The essential difference between the Lenoir and Otto engines 

 is that in the former the explosive mixture of gas and air 



'■ '^''The Gasi Engine." By Dugald Clerk. London-: Longmans, 

 Green, and Co. 1886. 



t We are indebted to the publishers of Mr. Clerk's book for per- 

 misiion to reproduce figs, l, 2, and 3. 



