1862.] on Meteorological Telegraphy, 447 



influence : and thus, as it were, forcing passages between streams of 

 chilling polar air that at the same time are moving in opposite and 

 nearly parallel directions. 



Sometimes their opposition is so equal, and equilibrium is so com- 

 plete, that a calm is the result, no sensible movement horizontally 

 along the earth's surface being perceptible. 



Self-registering barometers show the alterations in tension, or, so to 

 speak, the pulsations^ on a large scale, of atmosphere, by hourly marks ; 

 and the diagram expresses to a practised observer what the " indicator 

 card " of a steam cylinder shows to a skilful engineer, or a stethoscope 

 to a physician. 



Our own Islands have very peculiar facilities for meteorological 

 communication by telegraph, between outlying stations on the sea coast 

 and a central place — all being at nearly the same level, and nearly all 

 comparatively uninfluenced by mountain ranges. 



^nd now, the results are, that, having daily knowledge of weather 

 (including ordinary facts of a meteorological nature), at the extreme 

 limits and centre of our British Islands, we are warned of any great 

 change taking place ; the greater atmospherical changes being measured 

 by days — rather than by hours. Only local changes, however violent 

 they may be occasionally (and dangerous in proportion to their 

 suddenness and violence), — only such changes are unfelt at a distance, 

 and do not influence great breadths, — say, hundreds of miles in area, — 

 of atmosphere. 



Extensive changes, showing differences of pressure, above or below 

 the normal or mean level, amounting to an inch or thereabouts, are 

 certain to be followed by a marked commotion of the elements in the 

 course of a few days. If the fall has been sudden, or the rise very 

 rapid, — swift, but brief, will be the resulting elementary movement ; 

 if slow, or gradual, — time will elapse before the change, and the 

 altered state of weather will take place more gradually, but last 

 longer. 



Notice may thus be obtained, and given, a few hours, or a day, 

 or even some days, before any important change in the weather actually 

 occurs. 



Having such knowledge, it obviously follows that telegraphic 

 warning may be sent in any direction reached by the wires, and that 

 occasionally, on the occurrence of very ominous signs, barometric and 

 other — including always those of the heavens — such cautions may be 

 given before storms as will tend to diminish the risks and loss of life 

 so frequent on our exposed and tempestuous shores. 



It has been proved also, lately, that storms, indeed all the greater 

 circulations of atmosphere between the tropics and polar regions, have 

 an eastward motion, bodily, while circulating around a centrical area. 

 Within the tropics it is otherwise, or westward, till they recurve. 



In answer to a question from the Eoyal Commissioners on Lights, 

 Buoys, and Beacons, Sir John Herschel stated that — " the most im- 

 portant meteorological communication which could be telegraphed, 



Vol. III. (No. 35.) 2 h 



