ON GRAPHIC METHODS IN MECHANICAL SCIENCE. 413 



invaluable, having revealed on various occasions all sorts of defects in 

 the working of the engines, such as insutficient weight of flywheel, flaws 

 in the shafting causing extra friction and irregularity, and imperfect 

 action of the governors. None of these things would probably have been 

 detected except by a continuous graphic record, which, moreover, enabled 

 the defects of the changes introduced to be carefully studied by the 

 diagrams snbsequently obtained. 



An instrument belonging to the same class, but of entirely different 

 principle of action, has been designed by Messrs. Richard Freres under 

 the title of the ' Cinemograph,' of which a description is given in the 

 report of Colonel Sebert. 



An electro-cinemograph for electrically recording the speed or 

 number of revolutions of one or several engine shafts at a distance is also 

 described by the same makers as follows : — 



' This instrument is a combination of the speed indicator, previously 

 described, with an escapement system actuated by an electro-magnet. 



' It is set ready for work by merely winding up the string of the train 

 of wheels which causes the factors " Time" and " IS^umber of Revolutions " 

 to act upon one another. 



' Its installation is eff'ected in the following manner : — 

 ' On each machine a simple electric closing circuit arrangement for 

 each revolution is adopted. To each contact is attached two wires, one of 

 which is connected to a common return wire, the other being taken and 

 connected to a switch placed in the engineer's office. The switches are 

 arranged on a board, in front of which is placed on a bracket the electro- 

 cinemograph. This instrument is connected to the switches as well as 

 to the common return wire, and to a battery placed in the circuit. When 

 the engineer wants to ascertain the speed of any given engine, he, by 

 closing the circuit of the said engine with the switch, immediately sets 

 the cinemograph at work, and obtains a record on the diagram paper of 

 the number of contacts occurring at the shaft in the unit of time ; that is 

 to say, its number of revolutions per minute. The speed of every in- 

 dividual motor can thus be controlled. 



' This instrument is also used for measuring the speed of water- 

 courses, boats, or yachts by merely connecting it to contacts established 

 on a turbine of the Wolhmann system, or to an electric log of the 

 Fleuriais or other system.' 



Instruments for recording the flow and velocity of water have been 

 nsed, and perhaps the most important is the waste-water meter of 

 Mr. Deacon. This instrument enables any waste to be detected through- 

 out the whole of the system of the water supply of the City, and in a 

 continuous record night and day of the quantity of water passing. It 

 has been fully described in the ' Engineer ' and other jonrnals, to which 

 it will suffice merely to give reference.' 



(2) The principle of the second, or indirect class of velocity-recorders, 

 is to observe the slope made by the line as the pencil travels across the 

 surface moviug at a known rate. This is the case with a large number of 

 instruments, in which the revolutions of a turning vane move the pencil 

 over a clockwork drum. 



Another well-known type of the Osier anemometer operates on this 

 principle. So also do several kinds of engine-speed recorders ; but there 



' The Engineer, Nov. 26, 1886 ; Journal of the Society of Arts, May 17, 1882 ; 

 Proc. Inst. C.E., vol. xlii. pt. iv. ; Engineering, vol. xl. 1885, p. 488. 



