302 SCIENTIFIC APPARATUS. 



which, with its little vanes of aluminium, and its single large 

 recording dial, was brought out as Casella and Lowne's anemometer. 

 A very gentle breath of air will make itself felt on the light sails 

 of this miniature windmill, and it may, therefore, be applied with 

 advantage to test the ventilation of hospitals or other public 

 buildings. 



The late Professor John Phillips, of Oxford, proposed many 

 years ago the use of a single vane, which, suspended across the 

 path of the current, should show by. its deviation from the vertical 

 the comparative force of the wind blowing upon it. Mr. Dickin- 

 son, Inspector of mines in Lancashire, improved upon the instru- 

 ment by fitting it with a level, a counterpoise, and a graduated 

 arc, upon which may be read off the number of feet per minute at 

 which the current must be travelling, in order to blow out the 

 vane to a certain angle. 



A fan anemometer was invented by Professor Combes, of Paris, 

 which it \vould be interesting to compare in action with our own. 

 It is described in his " Exploitation de Mines," and is now stated 

 to be employed with satisfaction in many of the French collieries. 

 Dr. Robinson's anemometer has not, as far as the writer knows, 

 been employed underground, but the " Electric Velocimeter," 

 lately patented by Mr. F. Pastorelli, follows the same principle so 

 far as regards the relation between the revolutions and the velocity 

 of the wind. But instead of being satisfied with a record kept by 

 index dials attached to the instrument, the inventor transmits the 

 indications to a distance into the office, if thought desirable, 

 and this renders it possible for a manager to see at all times at 

 what rate his air current is travelling. Each revolution of the 

 cups, in fact, causes a contact to be made, and the receiving 

 instrument, containing an electro-magnet, has upon its face the 

 circles and indices for registering from 10 up to 10,000,000 feet 

 A Leclanche battery of six No. 2 cells is connected with it when 

 the instrument is to be set to work, but may be shut off by the 

 turning of a simple stop. 



