no 



SCIENCE. 



[Vol. II., No. 25 



odd, there exist three real points of inflection upon 

 the line u, so that in the last case there exists, as in 

 the case of cubics, an inflectional triangle. — {Nouv. 

 ann. math., Feb.) t. c. [105 



ENGINEERING. 

 Electric-lighting machines on shipboard. — 



More than a dozen of the steamers plying between 

 New Yorlv and Liverpool are fitted up with electric- 

 lighting machinery. Probably three times as many 

 are so fitted out on the various other lines of ocean- 

 going steamships. The British steamers are largely 

 supplied with the Siemens and Swan apparatus, but 

 the other systems are well represented. The electric- 

 light apparatus of the Arizona consists of two Sie- 

 mens compound dynamos, each sufficient to supply 

 current to three hundred high-resistance Swan lamps. 

 They are driven by a pair of ' Caledonian ' engines of 

 nine and a half inch cylinders and fourteen inches 

 stroke of piston. The two machines are mounted 

 upon a common foundation, and are set in such 

 manner that the driving-pulleys do not interfere with 

 each other. The belts are tightened by moving the 

 machines away from each other ; they are formed of 

 one continuous I'ope carried around each pulley ten 

 times. Both cabins, and the steerage as well, are 

 lighted by these machines. — {Engineering, May.) 



K. H. T. [106 



New engine for electric-lighting. — Mr. E. D. 



Farcot has designed a new form of compound engine 

 for electric-lighting machinery. It consists of two 

 cylinders, the larger set above the smaller. The space 

 between the two pistons is undivided, and is in com- 

 munication with the interior of the engine-frame, 

 and is never put in connection with the steam-supply 

 pipe. The steam first enters the small cylinder, and 

 is thence exhausted into the large cylinder, thus 

 driving the pistons, which are both on a single rod, 

 in opposite directions by a system of intermitted 

 expansion. The engine is thus seen to be of the 

 'Wolff system.' The space between the two pistons 

 is made to communicate with the larger space in the 

 frame, merely to secure a reduced variation of uncoun- 

 terbalanced pressure. No stuffing-box is needed in 

 this engine in any inaccessible part of the machine. 

 The valve-gear is of the plainest possible description, 

 and the whole engine is built with a view to simpli- 

 city and small cost in construction and operation. It 

 is intended to be driven up to four hundred revolu- 

 tions per minute. — {Publication industrielle, May.) 



R. H. T. [107 



Steam-jackets for steam-engines. — Hcrr Heim 

 reports to the German society of engineers the results 

 of experiments to determine the economy to be de- 

 rived by the addition of steam-jackets to various 

 forms of steam-engine. He finds that a six-horse power 

 portable engine, unjacketed, demanded an excess 

 of thirty-five per cent over the theoretical quantity of 

 steam that should have been required to do the work ; 

 an eighteen inch Wheelock engine required the same 

 excess over the calculated quantity. Both were non- 

 condensing. Condensing-engines experience a still 

 greater loss due to internal 'cylinder condensation.' 



Engines expanding ten times demand seventy-four 

 per cent excess; when cutting off at one-fifth, sixty- 

 two per cent; and expanding three times, fifty-five 

 per cent more than the calculated amount when they 

 are unjacketed. By adding a jacket, he concludes 

 that the loss can be reduced to sixty-four, fifty-four, 

 and forty-eight per cent. The effect of increase of 

 piston speed is similar to that of adding a jacket. 

 An engine at three feet, and at seven feet piston speed 

 per second, gave a record of loss amounting to ninety- 

 six and seventy per cent. The addition of the con- 

 denser causes increase of this loss. A twenty-inch 

 non-condensing engine, woi-king at five atmospheres 

 pressure, was provided with a condenser, and, while 

 the power was increased one hundred and forty per 

 cent, the waste was increased from forty-two to sixty- 

 two per cent. A hoisting-engine, working intermit- 

 tently, exhibited a loss of a hundred and forty-two per 

 cent of the weight of steam utilized. — {Mechanics, 

 June. ) E. H. T. [108 



AGRICULTURE. 



The gases evolved during the conversion of 

 grass into hay. — In a series of experiments on this 

 subject, conducted by Dr. P. F. Frankland and Mr. F. 

 Jordan, freshly-cut grass in quantities of five grams 

 each was allowed to stand in a glass tube over mer- 

 cury. The glass tube was filled with air, inert gases, 

 and experiments were also performed in vacuo. In 

 air all the oxygen was absorbed at the end of three 

 days, and 46% of carbonic dioxide was evolved. 

 At the end of thirty days the percentage of carbonic 

 dioxide reached 85.33, requiring a corresponding 

 amount of oxygen, which must have come from the 

 substance of the grass itself. Nearly pure carbonic 

 dioxide was evolved in an atmosphere of the same 

 gas, and a higher percentage seemed to be given off 

 in darkness than in sunlight, although the authors 

 were somewhat in doubt on this point. In an atmos- 

 phere of pure oxygen, the latter was absorbed com- 

 pletely in seven days, and the evolution of nitrogen 

 ceased when the oxygen disappeared. When the 

 experiment was conducted in an atmosphere of 

 hydrogen, 21.11% of this gas was replaced by car- 

 bonic dioxide at the end of three days. It thus 

 appears that certain constituents of the grass under- 

 go a rapid process of oxidation, and that nitrogen 

 is evolved as long as the atmosphere contains free 

 oxygen. The decomposition-products of grass, when 

 allowed to stand under water, were also examined. 

 The grass was first soaked in distilled water, and the 

 dissolved air removed with a Sprengel pump. Car- 

 bonic dioxide formed about 90 %, and hydrogen about 

 9 %, of the gases collected at the end of thirty days. No 

 gas was evolved when the formation of bacteria was 

 prevented by the addition to the water of phenol 

 or mercuric chloride. As the other products of the 

 fermentation, acetic and lactic acids, and probably 

 propionic acid, were identified. — (Journ. chem. soc, 

 June, 1883.) c. f. m. [109 



Absorption of moisture by soils. — Fisher finds 

 that, contrary to Knop's statement, the amount of 

 hygroscopic moistvire retained by a soil varies greatly 

 with the amount of moisture present in the air, as 



