6 



Hon. Kalph Abercromby. Relation between 



tropics, the author was led to consider the relation between the 

 intensity of the trough phenomena and the velocity of propagation 

 of the cyclone. For this purpose he examined the meteorograms, 

 published in the ' Quarterly Weather Reports ' of the Meteorological 

 Office, for all well-defined cyclones in the years 1872-76, and for part 

 of the year 1879. The intensity of the trough phenomena was 

 gauged by the amount of the effect of the squall on the barometric 

 trace, and the suddenness of the shift of wind at the same time. 



The result is given in the following table, by which it is evident 

 that there is a decided relation between the velocity of the cyclone 

 and the intensity of the trough phenomena. 



Table showing the Connexion between the Intensity of the Trough 

 Phenomena and the Velocity of a Cyclone. 



Year. 



Month. 



Day. 



V elocity 

 of cyclone. 



Miles 

 per hour. 



Intensity of 



trough, 

 phenomena. 



Remarks. 



1872 . . . 



Aug. 



10 



16 



Very slight 





35 ... 



Sept. 



25 



6 



No trace 





33 • * • 



Oct. 

 Dec. 



10 



8 



13 

 19 



Very slight 

 Slight 







33 



Aug. 



16 



16 



33 





1873 '. '. 



28 



16 



3> 







Sept. 



15 



19 



33 





1874.'.'.' 



April 



13 



27 



Moderate 







Aug. 



13 



13 



Slight 





... 



Oct. 



21 



24 



Moderate 





„ ... 



Nov. 



29 



12 



Moderate (Kew) 



Strong at Falmouth ; 

 earlier in course 

 when velocity un- 

 known. 



1875 . . . 



Jan. 



21 



48 



Strong 









24 



25 



Moderate 





... 



Sept. 



26 



29 



Strong 







Nov. 



19 



35 



Moderate 





1876 '. '. 



March 



12 



40 



Strong 





,, ... 



33 



14 



6 



Very slight 







33 



25 



10 



No trace 





1879 .' ! '. 



Dec. 



28 



70 



Very marked 



The Tay Bridge storm. 



The author has made many efforts to find traces of a central spot 

 of blue sky in the centre of a British cyclone. He has never 

 observed one himself, and though such cases have been reported, he 

 is not satisfied with the evidence. It is very common to see a patch 

 of blue sky directly after the passage of the trough, some distance 

 from the centre on the southern side of a cyclone, and soon to 

 experience wind and rain continuing for some time afterwards ; but 



