SCIENTIFIC NEV\^S. 



[March ist, 1887. 



der containing water. A falling weight attached to a cord 

 was made to rotate the blades, and as the mass of the 

 weight, as well as the distance through which it fell were 

 known, the work expended in driving the apparatus was 

 ascertained precisely. During the trial the temperature of 

 the water in the vessel was raised owing to the friction 

 produced by the blades, and in this way it was possible to 

 determine accurately the quantity of heat developed with a 

 given expenditure of power. This is known as the mecha- 

 nical equivalent of heat, and it at once helps us to under- 

 stand the presence of heat in the iron which was struck 

 with a hammer, and in the button which was rubbed. In 

 the case of the falling hammer, the energy of motion is 

 converted into heat energy when the hammer is suddenly 

 stopped by the iron. In like manner, the energy of motion 

 used in rubbing the button is converted into heat energj'. 

 It may be that in these cases the heat produced would not 

 be in a useful form, but it would be equivalent in quantity 

 to the mechanical energy expended, and if the iron or but- 

 ton is merely left to cool it will transfer its heat energy to 

 the surrounding air, or any body it may be in contact with. 

 Supposing, however, that instead of these two examples we 

 had two pieces of dry wood which were rubbed together 

 very quickly, the heat energy developed by the friction 

 would be so great that sparks would be given off; in fact, 

 by this means some savages kindle their fires. The ques- 

 tion, therefore, as to whether or not the heat is available for 

 practical purposes in no way affects the general law of the 

 transference of energy. 



So far we have only considered the interchangeability of 

 heat and mechanical work, but the same law holds good in 

 all other forms of energy. For instance, electrical may be 

 converted into mechanical energy, as when a flash of light- 

 ning destroys a church-steeple, or into heat, when a badly- 

 arranged conductor melts during the passage of the current. 

 A good illustration of the transformation of energy will 

 also be found in the , modern apparatus used for electric 

 lighting. The heat energy of the fuel in the boiler is con- 

 verted into mechanical energy at the steam-engine, and this 

 in turn is converted into electrical energy at the dynamo. 

 Finally, this is reconverted into heat and light energy at the 

 lamp, and in each of these transformations there is, after 

 allowing for waste due to friction and other causes, a de- 

 finite equivalent for the energy expended, an equivalent 

 which can always be accurately determined. 



Barium Hydrate from the Carbonate.— M. Hippolyte 

 Leplay, of Paris, proposes to make barium hydrate — a body 

 corresponding in its constitution to slaked lime — from barium 

 carbonate, by means of superheated steam. The barium carbo- 

 nate occurs as a mineral under the name of Witherite, near 

 Alston, in Cumberland, and Hexham, in Northumberland, and 

 many other places. Its decomposition is effected in one opera- 

 tion in a sort of cupola furnace ; and this is the novelty of the 

 process, somewhat similar proposals having been made by Jacque- 

 lain and Lenoir. The crushed carbonate is exposed on the 

 hearth to fresh steam, and then becomes partially decomposed, 

 the hydrate produced passing through a channel into an adjoining 

 basin, separated from the carbonate by a fire-clay partition. 

 Here the hydrate collects until it overflows the wall on the other 

 side, which is at a little lower level, and it then passes down a 

 slightly inclined hearth to the outlet, being all the time exposed 

 to the action of the steam. Leaving the cupola, it flows into a 

 basin filled with water, where the hydrate dissolves, and is after- 

 wards concentrated by the waste heat of the steam, the insoluble 

 carbonate which collects at the bottom beingi subjected to 

 another operation. 



Last month the Queen of the Belgians heard by telephone, in 

 her Palace at Brussels, an entire act of Faust, then being per- 

 formed at the Opera House in Paris. 



THE LIVING TORPEDO. 



THE Torpedo Fish, like the better-known Electric Eel, 

 is provided with very peculiar organs, by means of 

 which it is able at will to produce a discharge of electricity 

 sufficiently strong to paralyse fish passing over it. Thus, by 

 rendering small fish an easy prey, it obtains a supply of 

 food, and the organs may also serve as engines of protec- 

 tion from its enemies. 



The accompanying sketch shows the general arrangement 

 of the electrical apparatus when dissected out, the nerve- 

 trunks on both sides of the fish, connecting the organ with 

 the brain, being displayed by the removal of over-lying 



parts. These nerve-trunks are marked A, the brain is in- 

 dicated by B, and the mass of the electric elements by C. 

 Each organ C is made up of a number of parallel columns, 

 consisting of a series of elements set in rows one on the other. 

 The elements are united with one another by connective 

 tissue, which may be taken to represent the moist interme- 

 diate layers of the voltaic pile, and they all receive on their 

 under surfaces branches of the nerves A, which pass into 

 the organ. That face of the elements on which the nerves 

 ramify is the same in all the columns, and is always electro- 

 negative, the opposite free surface being electro-positive. 



The whole apparatus bears a most striking resemblance 

 to a voltaic battery. 



