VI. MACHINERY. 403 



2045f. Model of Circular Shears, with concave cast frame. 



John Tille, Prague. 



These two models, the circular cutting blades of which are fastened on 

 spindles, and put in motion by means of wheels and cranks, illustrate chiefly 

 the solidity and elegance of the concave casting as compared with the ribbed 

 casting. 



2046. Circular Knitting Machine. (J. A. Tielen's Patent, 

 1842.) Bennet Woodcroft, Esq., F.R.S. 



2047. Models of Chinese Agricultural Implements (9), 

 small mill, &c. Bennet Woodcroft, Esq., F.R.S. 



2048. Model for showing the Curves of Screws. 



Bennet Woodcroft, Esq., F.R.S. 



2050. Traction Dynamometer, used for ascertaining the 

 draught of carts, waggons, and all agricultural implements that 

 are drawn by horses. Also, for determining the resistance of 

 roads and streets. Royal Agricultural Society of England. 



The instrument is harnessed just like a horse to the implement it is desired 

 to test, and being itself drawn along by one or more horses it registers the 

 total work done in passing over any given distance, the mean and extreme 

 tractive force, the pressure on the back of the horse, and the lateral pressure 

 in such implements as reaping and mowing machines. First used at Bedford, 

 1874. Designed and made for the society by its consulting engineers. See 

 Journal of the Koyal Agricultural Society of England, No. XX., part 2, page 

 678. 



2051. Appold Friction Dynamometer, of 100 horse-power, 

 used for measuring the work done by steam engines and other 

 prime movers. Royal Agricultural Society of England. 



The prime mover to be tested is coupled to the main shaft of the dynamo- 

 meter, the friction breaks of which are loaded in proportion to the power it is 

 desired to develop. The instrument registers the number of revolutions made 

 in a given time, and this, together with the known weight on the breaks, fur- 

 nishes the data for calculating the work done by the prime mover. This 

 powerful instrument was constructed by the consulting engineers of the 

 society, for the trial of steam ploughing and traction engines at Wolverhamp- 

 tonin 1871. 



2O53. Pneumatic Pump, with taps. Invented by 'sGrave- 

 sande. Professor Dr. P. L. Rijke, Leyden. 



The taps are at each stroke of the piston turned 90 by an appliance in 

 the form of a cross fixed to the handle. (See 'sGravesande's " Physices 

 Elementa Mathematical ed. III. vol. II., p. 591.) 



2O53a. Pneumatic Intercepting Apparatus for sending 

 and receiving message carriers in pneumatic despatch tubes of 

 3 inches diameter, to be worked on the circuit system. 



Messrs. Siemens Brothers. 

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