NEW FORM OF ANEMOMETER. 41 



pressure of the current of air. There is nothing to move backwards 

 and forwards, and therefore friction is out of the question. I can 

 measure the rate of air, supposing it is going at the rate of 4 feet a 

 second, and can tell it is not going at the rate of 4 feet I inch a second. 

 When it gets down to a very low speed, below 12 inches a second, its 

 action is very feeble, and that is the weak part of the instrument, but 

 when it gets up to anything like 4 feet per second you can tell with 

 great accuracy. 



THE PRESIDENT : I have now to convey the thanks of the meeting 

 to all those gentlemen who have favoured us with communications 

 this afternoon. It is remarkable to observe how subjects connected 

 with light have come forward. They were dealt with this morning 

 and have again reappeared for our consideration this afternoon. The 

 mode in which the different branches of optics which turned up this 

 morning, in the first place dispersion, then fluorescence, then inter- 

 ference and polarisation, keep cropping up here and there, shows how 

 very much all these different branches of the subject, notwithstanding 

 the care with which they are kept apart, as subjects of actual research, 

 do flow into one another, and by their mutual interference throw light 

 upon one another. The arrangement for our next Physical Conference, 

 which takes place on the iQth, are nearly complete, but I hope the 

 audience will always remember that we are indebted very much to 

 the voluntary assistance of those who are good enough to make 

 communications, and that our arrangements are, at all times, liable 

 to some kind of disturbance. Nevertheless, I feel quite sure that we 

 shall never lack for interesting matter during the Conferences. 



