IV. ANEMOMETERS. 695 



each -J- of a mile, indicated by the revolutions of the cup^, may be trans- 

 mitted electrically and consecutively to the receiving instrument. 



This instrument has the ininimuHi amount of friction. The cup arrange- 

 ment can be placed in any distant and convenient position, and the receiving 

 instrument in the observatory. It is portable, being of small dimensions. 



2845. New Portable Anemometer, by Francis Pastorelli, 

 for measuring accurately the velocity of the air or wind, specially 

 adapted for scientific travellers and explorers. Francis Pastorelli. 



It consists of four small hollow hemispherical cups (Dr. Robinson's form) 

 fixed to a vertical axis ; the lower end has an endless screw. This works a 

 wheel, the complete revolution of which is equal to ~ of a mile. Its action is 

 conveyed to others that carry indexes over divided circles on the face of the 

 dial, which is mounted on a circular box fixed on a metal base ; readings can 

 be taken from -^^ up to 1,000 miles. Its weight, 1| Ibs., and it packs in a 

 mahogany case about 4^- inches square. 



This is a most sensitive instrument ; its indications are as accurate as those 

 of the large kind. 



2845a. Anemometer, with shaft whose length can be 

 adjusted to suit different stations, and with dial reading to 10,000 

 miles, constructed for stations of the 2nd and 3rd order connected 

 with the Canadian Meteorological service, 



G. T. Kingston, M.A., Toronto, Canada. 



This instrument is designed to reconcile adequate exposure of the hemi- 

 spheres with accessibility of the dial. 



A short spindle bearing a small set of Robinson's cups is connected with a 

 horizontal cogged wheel resting on friction rollers, and with a long shaft 

 suspended from its centre, as in the anemographs of the British observatories. 

 It is contrived so that the shaft may make 101 complete turns for 200 miles 

 of wind. 



The mode of recording the miles is as follows : 



At the lower end of the shaft is an endless screw which acts on the circum- 

 ferences of two toothed wheels of equal diameter, turning in vertical planes 

 about a common axis, and having 100 and 101 teeth respectively. 



From the centre of the back wheel (that of 100 teeth) projects forwards a 

 short hollow pin which incloses and works on a solid pin fixed to a support 

 behind the back wheel. 



The front wheel (that of 101 teeth) which turns 011 the above named hollow 

 pin, and slides closely on the face of the back wheel, has a graduated ring on 

 its face, containing 100 divisions. The outer ends of the lines of graduation 

 indicate miles, while the inner ends of the same lines, reckoned in the reverse 

 order, indicate hundreds. 



The endless screw, at every turn, causes both wheels to advance two teeth, 

 so that for 100 miles the front wheel makes one complete turn, or 100 divi- 

 sions, while the back wheel make one complete turn and one tooth, and thus 

 advances one division with respect to the front wheel. The miles up to 100 

 are shown by a fixed pointer, and the hundreds by a pointer attached to the 

 end of the hollow pin. 



For fractions of a mile there is a contrivance which needs adjustment at 

 each observation. 



A correction of 1 per cent, nearly should be subtracted from the fractional 

 parts. 



If the anemometer be two distant from the observer's office to allow the 

 dial to be read conveniently with the required frequency (if, for instance, it 



