250 



REPORT 1844. 



compared. Thirdly, there should be some means of registering the actual 

 pressure of the current on a given area, either by a pressure-plate or a column 

 of fluid on Lind's principle ; the former is perhaps to be preferred, as ad- 

 mitting of a greater degree of precision. There should also be a rain-gauge 

 connected with the instrument, and the whole should be regulated by a good 

 time-keeper, so as to give a constant register of these elements for known 

 periods of time. 



I am not exactly prepared to say at present how the mechanical detail of 

 such an anemometer could be best carried out, so as to get the machine 

 within a small and convenient compass ; but from some considerations which 

 I have been led to, I do not think it would be difficult to accomplish. In 

 support of this opinion, I venture to submit to the Association the follow- 

 ing most ingenious arrangement, kindly communicated to nie by the Rev. 

 W. Foster of Sturbington, near Portsmouth in Hampshire, and which com- 

 pletely embraces some of these views. The general nature of this machine 

 will be easily apprehended by reference to the annexed cut. 



A is a cross horizontal fly of three feet in diameter, having four vanes, a, b, 

 c, d ; these vanes are six inches square, and are so contrived as to cause the 

 fly to revolve in one direction only. By the revolution of this fly motion is 

 communicated to an endless screw B at the termination of the vertical shaft 

 A B attached to the fly, and passing through the roof of the house at D the 

 fly is supported on the hollow tube A D. By means of the endless screw at 

 B a train of mechanism is put in motion, which motion is finally communi- 

 cated to the axis g h, and by this through another endless screw, not shown 

 in the figure, to the disc P, so that this disc, which is twenty-two inches in dia- 

 meter, is caused to revolve slowly in a horizontal plane, hence the motion of 

 P registers the revolutions of the fly A, the revolutions of which may be in 

 any convenient proportion to those of the disc 1 : 10000 or 1 : 20-000. 



R is a vane, and R S a vane rod, working also through the roof at F, byi 

 which a similar horizontal disc S is turned about a centre; this disc is nine 

 inches in diameter. M is a rain receiver, and M N a pipe by which the rain 

 descends into a gauge N ; this gauge consists of two compartments in the 



