78 SEC. 3. MEASUREMENT. 



gearing. It is plain that this meter really registers the true velocity of the 

 water, and taking, moreover, in consideration the lightness of its different 

 parts and the transmission of the speed of the float by means of magnets, it 

 will be found to be a very correct and sensitive meter, of simple and durable 

 construction. 



399a. Water-meter, with electrical numbering apparatus, 

 according to Amsler's latest construction. (See description.) 



Polytechnic Schoal at Aix-la-Chapelle, O. Intze. 



If the instrument makes 100 revolutions the electric current will be closed 

 by a contact, and the chime work will be kept in motion during some revolu- 

 tions of the instrument ; it will not be necessary, therefore, in measuring the 

 velocity in water-courses, to pull the instrument out of the water, but only to 

 note the time which passes from one signal to the other. By experiments it 

 must be ascertained what velocities of the current of the water correspond 

 to certain intervals of time of the electric signals. 



40O. Patent Electric Velocimeter, invented by Francis 

 Pastorelli, arranged for water currents, and for ascertaining the 

 speed of vessels, or rate of their motion through water. It consists 

 of three parts. Francis Pastorelli. 



1 . Four hemispherical cups are fixed to the end of four strong metal arms 

 (at a distance of 90 apart) that radiate from a central boss, which are mounted 

 on a horizontal axis at right angles in a framework of metal, or other material, 

 so that they may freely revolve when placed in the water. The horizontal 

 axis has fixed to it a point or piece of platina ; upon this work pressing points 

 or surfaces, which can be made of any form, circular or otherwise ; each revo- 

 lution of the axis causes -a contact to be made. 



2. The same receiving instrument, as used for the mining instrument. 



3. A Leclanche battery, as used for the mining instrument. 



The receiving instrument can be placed in any convenient position on 

 board. 



N.B No. 1. This part of the instrument is intended to be fixed at any 



desirable and convenient part of the vessel, or it may be arranged to throw 

 overboard ; under such conditions it will give more accurate indications than 

 the logs now in use, for it is not affected like them in their motion by depth, 

 or the increasing density of water ; assuming that corrections be applied for 

 force and direction of currents, with respect to the course or line of motion, 

 I think the errors would not be found to exceed 5 per cent. 



402. Apparatus for indicating the Speed of a Ship by the 

 aid of Electricity. Bennet Woodcroft, F.R.S. 



409. A Rhysimeter, without frictional parts, for measuring 

 the speed of water or other liquids whether in pipes or open 

 channels. Alfred E. Fletcher, Liverpool. 



B. ANEMOMETERS. 



408. An Anemometer, without frictional parts, suited to 

 measure the speed of air or gases, even when highly heated, or 

 when contaminated with smoke or corrosive vapours. Used by 

 H.M. Inspectors of Alkali Works. Alfred E. Fletcher, Liverpool. 



