1876.] Report of the Meteorological Committee, 201 



This latter circumstance, however, appears to be a local pecu- 

 liarity, and it is probable that if the weather were studied over a 

 wider area, as in the synoptic charts of Capt. Hoffmeyer, or those 

 projected, but not yet carried out, by the United States Signal 

 Office, light would be thrown upon it. It is certain that a mo- 

 tion westward does sometimes occur even over these islands, as 

 well as in lower latitudes, as, e. </., over Turkey in Asia, from 

 Bagdad to Salonika, Nov. 3-6, 1869. 



" The appearance of secondary cyclones in connexion with larger 

 disturbances of the same nature is gradually attracting more and 

 more attention. These systems are imperfectly developed, inas- 

 much as, generally speaking, they exhibit no easterly winds of 

 much force, manifesting themselves on the southern side of their 

 primaries, and intensifying the violence of the westerly winds 

 which blow under such circumstances. 



" It must be admitted that, not unfrequently, the arrival of one 

 of these satellite depressions, in advance of a more serious storm, 

 has enabled the Office to give timely warning of the latter. 



" The comparative rarity of the easterly winds in our cyclonic 

 storms is probably traceable to the constant existence of an area 

 of deficient pressure near Iceland, which renders the formation of 

 steep gradients for easterly winds an unusual phenomenon. 



" There appear to be some indications of principles by which we 

 can recognize whether or not a cyclonic disturbance is speedily to 

 be succeeded by another. 



" If, after the centre of a depression has passed over us, the shift 

 of wind and fall of temperature causes a great clearness of the 

 air, intense radiation occurs at night, the thermometer on the 

 grass falling 10° to 14° below that in the shade 4 feet above the 

 ground. Under such circumstances it has been noticed that the 

 advent of a new depression is imminent. When, however, the 

 series of successive depressions has ceased for a while, the wea- 

 ther clears much less rapidly, and radiation is not nearly so 

 marked. 



" On the whole thus much may be affirmed, that it is to the general 

 conditions of atmospherical pressure over as large an area as pos- 

 sible that we are to look for an insight into the probable changes 

 which are likely to ensue. To this subject I shall shortly 

 recur. 

 " III. Temperature. — As regards the relation of this element to atmo- 

 spherical disturbance, there are no definite principles which can 

 be said to be generally admitted as true. This may be gathered 

 from the almost total silence on this subject on the part of those 

 who replied to the circular of the Leipzig Storm- Warning Com- 

 mittee in 1872. 



