2 



Description of an Automatic 



the only alternative is to substitute some mechanical means 

 for the labor of personal observation ; in short, to make the 

 instrument record its own changes. If this can be done in 

 a single instance, it can be done continuously. 



TJne only method by which this has been hitherto at- 

 tempted with success has been by the application of pho- 

 tography. This, though a very considerable advance, and 

 probably all that could be desired in respect of continuity 

 and accuracy of the record, is liable perhaps to the objec- 

 tion that it is too complicated a process for general use. 

 If we consider the skill requisite in the preparation of the 

 paper, the delicacy of manipulation involved by the appa- 

 ratus, and the labor of interpreting the results, as compared 

 with the average capacity and means of the great number 

 of observers desired and likely to volunteer or be employed 

 for such a purpose, it would seem that a simpler process 

 is both desirable and necessary. This it has been my in- 

 tention to furnish, and with what success remains for time 

 and experience to determine. The importance of the sub- 

 ject will justify me perhaps in presenting some account of 

 the new method. 



The problem to be solved, was to cause any meteorolo- 

 gical instrument, by means of suitable mechanism, simply 

 and effectually to record its own changes. The instrument 

 selected for experiment was the barometer. "When any 

 delicate instrument is made to record its own changes by 

 mechanical means, the chief difficulty is that of getting 

 sufficient power for the mechanism attached to make a 

 distinct and continuous record, without taking a percepti- 

 ble amount of force from the instrument itself, and thereby 

 vitiating the results. The use of electricity naturally sug- 

 gested itself as the best means of overcoming this obstacle. 

 This agency has not as yet been made economical or cer- 

 tain as a motor, but is chiefly valuable in controlling power 

 obtained through some other means. By it, as may be 

 seen in its application to clock work, and in the telegraph, 



