Rear-Admiral FitzRoy on Meteorological Telegraphy. 401 



with the ' Law of Gravitation ;' the grand results of both are exceed- 

 ingly simple, but the minor details become more and more compli- 

 cated in proportion to their minuteness*." 



Consecutive storms, at the meetings of main currents in zones of 

 latitude at certain periods, have had appearances of continuity. The 

 familiar instance of the ' Charles Heddle ' has so often been adduced 

 as proof of continuing circuitous action or gyration, that it may 

 seem injudicious to doubt the evidence ; but knowing how frequently 

 circuits or cyclones succeed each other rapidly, and how unreliable 

 are some of the earlier logs of events in a storm written after its 

 cessation, especially respecting directions of wind and courses 

 steered, when waves and storm-blasts were the guides, not the 

 oscillating compass (if indeed that had not been washed away, as in 

 the ' Charles Keddle's ' case), it does not appear accordant to expe- 

 rience and enlarged acquaintance with the subject to imagine that 

 such atmospheric eddies are sui generis, erratic, and so considerably 

 independent as to cross a wide ocean. 



When opposing currents meet, their masses must continue in 

 motion a certain time, either rotating or ascending, or going onward 

 horizontally in combination. 



Masses of air, either of polar or tropical origin, so to speak 

 returning, when driven back by stronger opposition, at first and for 

 a certain time retain the characteristics of their peculiar and very 

 different natures. 



In our latitudes there is a continuous alternation of air-currents, 

 each specifically different, and denoting approach by marked charac- 

 teristics ; and we have proved, by successive series of simultaneous 

 statical observations over a wide range, embracing Scotland, Ireland, 

 all England, and adjacent islands, that while these alternating or 

 circuitously moving currents are thus incessantly passing, the whole 

 body of atmosphere filling our temperate zone is moving gradually 

 towards the east at an average rate of about five geographical miles 

 an hour. 



During strong westerly winds this eastward motion is greatly 

 increased : and in easterly gales it is proportionally diminished, as 

 measured by its passage along a horizontal surface of earth or ocean. 

 Knowing these circumstances, and having accurate statical observa- 

 tions of these various currents at selected outlying stations, showing 

 pressure (or tension), temperature, and relative dryness, with the 

 direction and estimated horizontal force of wind at each place simul- 

 taneously, the dynamical consequences are already measurable 

 approximately on geometrical principles ; and, judging by the past, 

 there appears to be reasonable ground for expectation that soon 

 meteorological dynamics will be subjected to mathematical analysis 

 and accurate formulas. The facts now weighed and measured 

 mentally, in what may be correctly called " forecasting ? ' weather, 

 are the direction and force of each air-current or wind, reported 

 telegraphically to the central station in London, from many distant 



* W. Stevenson, of Dunse, 1853. 

 Phil Mag. S. 4. Vol. 23. No. 155. May 18G2. 2 E 



