TRANSACTIONS OF THE SECTIONS. 51 



by them in their observatories, its essential features being- identical with the 1858 

 instrument. 



Experience has shown that under most circumstances the working of this instru- 

 ment leaves but little to be desired, but that in situations where it is necessary 

 to place the recording-apparatus at a considerable distance from the external 

 driving parts of the instrument its action is subject to irregularities, due principally 

 to the yielding of the long, light shafts which have then to be employed ; and it is 

 to meet such cases that the modification now brought before the Association has 

 been devised by me. 



No originality is to be found in the adaptation of electricity to the purpose of 

 registering the ^vind ; numerous arrangements have been made by which it can be 

 accomplished. I need only allude to Secchi, Crossley, Gordon, Hall, and others 

 who have constructed instruments which do it. 



In my plan for the velocity-recording apparatus, where rotation in one direction 

 only is required, I employ, first, a simple contact-making key, on the shaft car- 

 rying the Robinson's cups, which transmits a short current every time the cups 

 complete a revolution. This current is then led by means of a wire to the 

 recording-apparatus placed at any distance ; and there, by means of an arrangement 

 of electromagnets and escapement similar to that employed in the step-by-step 

 telegraph instrument, successive currents produce the continuous rotation of a 

 wheel. 



This wheel being put into connexion with the train of wheelwork at present 

 existing, eventually drives the pencil round and recoi'ds the wind's movement 

 upon the paper. 



The Direction-apparatus. — Registration of the wind's direction by means of 

 electricity is somewhat difficult of execution by reason of the fact that rotation of 

 the wind-vane occurs sometimes in a positive or right-handed direction, veering 

 from and through E. and S., and sometimes vice versa, or from N. through W. to 8. 

 Various plans have been devised for accomplishing the thing desired, requiring 

 wires varying in number from four to thirty-tsvo. In the instrument now described 

 two only are needed, one of which is employed to transmit the rotary motion of tlie 

 vane to the recording-pencil, the other determining the direction in which the 

 rotation is to take place. 



A toothed wheel in electrical communication with a battery is fixed upon the 

 vane-spindle, and a contact-breaker so arranged that a current is sent to the re- 

 cording-apparatus every time a tooth passes. 



Every current transmitted causes a wheel in the registering-apparatus to rotate 

 through a small arc, always of course in the same direction. 



In order to record buckinr/ of the wind, the second wire must be made use of. 

 Above the contact-making wheel on the vane-spindle, and turning loosely in it, a 

 small insulated metallic collar is fitted, immediately over which there is a metal 

 disk fastened to and turning with the shaft; a stud projecting from the underside 

 of this disk plays between two stops on the collar, one of which is a conductor, the 

 other being an insulator. 



The play of the stud between the two stops is merely sufficient to make and 

 break the electrical contact. 



The wire from the metallic stop is led to an electromagnet fixed above the 

 recording-apparatus. A lever-clutch, moved by the armature of the magnet, acts 

 upon the driving-spindle of the pencil cylinder, raising it when a current passes, and 

 so bringing the lower of two mitre wheels fixed iipon the spindle into gear with 

 the mitre wheel turning the cylinder, on its under side, and causing it to rotate 

 when the spindle is turned. When the current is discontinued, a spring draws the 

 spindle downwards, and the top mitre wheel is brought into gear with the upper 

 side of the pencil-wheel, whilst the lower one is set free; continued rotation of the 

 spindle has now the effect of turning the pencil in the reverse direction to that 

 in which it was previously moving. 



Under ordinary circumstances this will be the position maintained ; the vane-stud 

 being in contact with the insulating stop, no current passes ; should, however, the 

 wind veer against the sun, the movement of the vane will make electrical contact, 

 the sliding shaft be lifted, and, the lower wheel coming into gear, the rotation of 



4* 



