Augtist 2, 1877] 



NATURE 



275 



thus obtained not only verify the scale of comparison based on the 

 5th power of the dimension, but the* nlso furnish a starting-point 

 by which to quantify the dimensions of the instrument which will 

 be required to deal with anv given horse-power delivered wiih 

 a certain number of revolutions per minute ; and it thus ap- 

 pears that to command the measurement of 2,000 horse-power 

 ("elivercd with 90 revolutions per minute (a fairly typical speed 



for the power), an instrument of the dimensions fhown in the 

 accmpanying drawings will suffice, the turbine being 5 ft. in 

 d '.in Mtr, and beinj: in fact a duplicate turbine, or formed with 

 twii faces, with a double-sided casing to match. This two-faced 

 atrani; men", it may be added, while it supplies a doubled cir- 

 cumferential reaction with a given diameter, has tl e advantage 

 of obliterating all mutual thrust on the working parts ; the 



Integrating apparat 



centrifugal forces of the double set of vortices pressing with 

 equal intensity on the two internal opposite faces of the rigid 

 casing. 



As regards condition No. 2, the theory suggests that, by con- 

 tracting the internal waterways, that is I'u say the passages 

 through the cells in the turbine and the casing, and thus inter- 

 cepting the free vortical rotation, all other things remaining the 



M 



same, the moment ol reaction due to a given speed ot rotation 

 could be greatly reduced. 



The experiments with the models fully bore out this anticipa- 

 tion also, and proved that, by the very simple arrangement 

 shown in the drawings, the reaction with any given speed of 

 turbine rotation can be reduced with a perfectly graduated 

 progression in any required ratio down to I-I4th, the object 



Integriiiing apparatu: 

 being efiected by advancing, from recesses in the casing abreast I of dealing with an engine of 2,000 horse-power, making ninety 



ot the two opposite quadrants in each turbine, a lunette-shaped 

 sliding shutter of thin metal, so fitted as to be carried forward 

 (by a screw motion governed from the outside) along the divisional 

 plane between the turbine cells and the casing cells. The 

 intensity of the reaction is thus brought completely and easily 

 under command ; and in virtue of it, it follows that the instrument 

 represented in the drawing, which, as already stated, is capable 



revolutions per minute, is also capable of dealing \\ ith one of only 

 340 horse-power, making 120 revolutions per minute. And as the 

 reaction of the instrument vanes as the square of its speed of 

 rotation, and the horse-power delivered through it consequently 

 varies as the cube of the speed of rotation (that is 10 saj', with 

 a given setting of the shutters), and as, moreover, this law of 

 variation is somewhat the same as that which the engine itself 



