July 3, 1884] 



NA TURE 



out of them quite unaltered. However, so as to leave no 

 doubt as to the accuracy of the readings of the ergometer, 

 the instrument is finally calibrated by another method, 

 which is new ; it is as follows : — 



Let a prime-mover (a water-wheel appears to be the 

 most steady) drive the transmission ergometer, and let 

 the ergometer drive a pulley on a shaft embraced by a 

 suitable friction ergometer, such as a Prony brake or an 

 Appold's brake, and let the work done against friction be 

 calculated. This should agree with the results of the 

 transmission machine. If it does, we may conclude that 

 it has been correctly calibrated. The advantage of this 

 method is that the transmission machine is tested while 



running in its usual condition. When testing a dynamo 

 care should be taken that the speed indicator be well 

 attached to the shaft the velocity of which it is measuring. 

 A piece of coiled spring, such as is used in a dentist's 

 lathe, answers well to connect it to the machine. 



The leading feature of this instrument is the position of 

 the spring in it. The axis of the spring and of the shaft 

 coincide ; the result of this is that it is hardly at all 

 affected by centrifugal force. When springs of slight pull 

 are used and the ergometer is driven at a great velocity, 

 the deformation is considerable, and would introduce 

 considerable error into the result. 



The deformation of the spring has been fully appre- 



ciated by Schuckert, and therefore he has placed the 

 spiral springs of his ergometer in cylindrical cases. 



When the spring is placed with its axis coincidental 

 with that of the machine, no such error can be introduced, 

 and the friction of a spring against a case is avoided. 



When a continuous record of work is required, a cylinder, 

 not shown in the figure, is placed at the dial end of the 

 instrument, and is driven at a speed proportional to the 

 speed of driving. It carries a band of paper which 

 receives a continuous trace from three self-feeding ink- 

 pens : one pen is attached to the lever which is moved by 

 the extension of the spring, and it writes ordinates directly 



proportional to the amount of extension of the spring at 

 any instant ; the second pen, attached to the lever of an 

 electro-magnet magnetised by a current controlled by a 

 seconds pendulum, describes a V-shaped mark at each 

 second ; the third pen traces a datum line to which the 

 ordinates are perpendicular. The area traced out is of 

 course the product of the two variables, and is propor- 

 tional to the total work transmitted. The recording drum 

 may be made to revolve at any convenient ratio to the 

 revolutions of the belt wheels. We are indebted to Mr. 

 Smith for the loan of the figure which illustrates this 

 notice. 



NOTES 



We are authorised to state that there is no truth in the rumour 

 that Mr. Oscar Dickson intends to equip an Antarctic Expedition 

 under the command of Baron Nordenskjbld. 



The Rev. Dr. Salmon, Regius Professor of Divinity in Trinity 

 College, Dublin, has been selected by the Institute of France to 

 fill its vacant foreign membership. 



According to the constant practice of the French Academy 

 of Sciences, the seat occupied by M. Jamin in the Section of 

 Physics is considered as vacant, and a new election will take 

 place. 



A meeting was recently held in the Hall of the Institution of 

 Civil Engineers, Great George Street, Westminster, to consider 

 what steps should be taken to raise an Engineers' Memorial to 

 the late Sir William Siemens. Sir Joseph Bazalgette, as Presi- 

 dent of the Institution, was asked to preside. The Chairman 

 pointed out that a general desire had been expressed among 

 engineers that some memorial should be raised as a recognition 

 of the great merits and important services rendered to engineer- 

 ing by Sir William Siemens. It has been ascertained that it 

 would be agreeable to the authorities of Westminster Abbey that 

 a window should be placed in that building to the memory of the 

 deceased. Possibly the cost of such a window might amount to 



