GEEENWICH— LIVEEPOOL. 



203 



onr Anti-Cyclones is subject to modification according to the seasons. In 

 summer, brilliant weather usually accompanies them, and in the central 

 districts particularly the sky is often nearly or totally devoid of cloud ; at 

 other times light fleecy cirrus, whose motion is extremely slow, is the 

 principal cloud visible. In winter, dry weather stratus is the most common 

 form of cloud, occasionally covering nearly the whole of the Anti-Cyclonic 

 system with an unbroken canopy. 



(133.) From statistics, recently prepared at the Meteorological Office, 

 of Gales and Storms occurring in the British Isles during the fifteen years 

 1870 — 1885, it appears that the most stormy area is at the entrance of the 

 English Channel. Agreeing with the experience of the North German 

 Lloyd steamers, as described on page 196, the summer is shown to be 

 nearly free from Storms, they being almost exclusively confined to the 

 winter half-year, the latter half of January being the stormiest period of 

 all. Contrary to the general idea, there is no marked stormy period at 

 either Equinox, though the frequency increases after the autumnal Equinox, 

 and decreases from January towards the vernal. 



(134.) Greenwicli. — The following Table gives the Mean Annual Number 

 of Days of Prevalence of the Different Winds during the forty-nine years 

 from 1841 to 1889, from the Eecords of the self-registering Osier Anemo- 

 meter at Greenwich Observatory.* 



N. 



Mean 1841—1864 39 



„ 1865—1889 40 



», 1841—1889 40 



(135.) Liverpool. — At the former Liverpool Observatory', near the 

 Waterloo Dock, an Anemometer, the invention of Mr. A. Follett Osier, 

 F.E.S., registered the force, or rather the motion and direction of the air, 

 for the years 1852 — 1855. The lines thus drawn by the machine itself are 

 reduced on the adjoining diagram, and represent the actual direction and 

 distance, according to scale, travelled by the wind over the instrument. 

 Upon looking at these lines, except the general tendency to the Eastward, 

 there is no similarity between the years; yet, by taking the absolute motion 

 throughout the year of the wind from any quarter, and forming a single 

 diagram, there is seen to be a remarkable identity in them all. 



Thus, the main direction of the wind in 1854 was rather to the Southward 

 of West; in 1852, it was to N.W.; and in the other two years, although 

 to the West, yet the wind was very devious. 



Notwithstanding the wide difference in the lines formed in these different 

 years, yet if the whole amount of wind in each year is arranged graphically 

 for each point of the compass, they are very similar to each other, showing 

 that a fixed law prevails ; which is still more evident if the duration of 

 their prevalence were taken instead of their quantity or velocity. This is 

 shown by the wind-stars on the diagram. 



• On the Relative Prevalence of Different Winds at the Royal Observatory, Greenwich, 

 1841—1889, by William Ellis, F.R.A.S., published in the Quarterly Journal of the 



Royal Meteorological Society, 1890, pp. 221—224. 



