Current of Air flowing past heated Platinum Wires. 255 



be anticipated, as wire No. 11 was not heated in the deter- 

 mination of the curve 5 in fig, 6. Finally, in this connexion 

 it may be remarked that, as seen from fig. 6, the initial sen- 

 sitivity of the arrangement employing three wires in each 

 arm, as already explained, is practically identical with that 

 of the two-wire arrangement. This initial decrease in the 

 anticipated sensitivity is, of course, attributable to the fact 

 that No. 6 wire, with its small initial rate of increase of 

 temperature with increase of the impressed velocity, is in- 

 cluded in the second group of wires constituting such a device. 



100 120 140 

 DEFLECTION. 



The calibration curves given in fig. 7 were obtained by 

 inserting the single wires indicated in the arms of the bridge, 

 intermediate wires functioning as a heating coil. In the 

 case of the full-line curves in tio-. 7, all remaining wires of 



zee 



