THE BAROMETER AND THE WEATHER. 149 



(if nothing else interferes) a flow of air from Dublin to- 

 wards Galway. It is also evident that, in order to tell 

 what else may interfere, we must know the atmospheric 

 gradients beyond and around both Dublin and Galway, and 

 for considerable distances. 



We are now beginning to obtain such information by 

 organizing meteorological stations and observatories, and 

 transmitting the results of simultaneous observations by 

 means of the electric telegraph to certain head-quarters. 



The subject is occupying much attention, and the mana- 

 gers of those splendid monuments of British energy our 

 daily newspapers are publishing daily weather charts, and 

 therefore a few simple explanations of the origin, nature, 

 and significance of such charts will doubtless be appreciated 

 by our readers. 



The grand modern improvement of the barometer, the 

 thermometer, the anemometer, the pluviometer, etc., is 

 that of making them "self- registering." We are told that 

 Cadmus invented the art of writing, and we honor his 

 memory accordingly. But he ventured no further than 

 teaching human beings to write. Modern meteorologists 

 have gone much further; they have taught the winds and 

 the rains and the subtle heavings of the invisible air to 

 keep their own diaries, to write their own histories on 

 paper that is laid before them, with pencils that are placed 

 in their fleshless, boneless, and shapeless fingers. This 

 achievement is wrought by comparatively simple means. 

 The paper is wound upon an upright drum or cylinder, 

 and this cylinder is made to revolve by clock-work, in such 

 a manner that a certain breadth travels on during the 

 twenty-four hours. This breadth of paper is divided by 

 vertical lines into twenty-four parts, each of which passes 

 onward in one hour. Connected with the barometer is a 

 pencil which, by means of a spring, presses lightly upon 

 the revolving sheet, and this pencil, while thus pressing, 

 rises and falls with the mercury. It is obvious that, in 

 this manner, a line will be drawn as the paper moves. If 

 the mercury is stationary, the line will be horizontal only 

 indicating the movement of the drum ; if the mercury falls, 

 the line will slope downwards ; if it rises, it will incline 



