128 Mr. W. R. Birt on Atmospheric Waves. 



Seventh zone below the crest. S.W. wave. 





Barom. 



Direction. 



Force 



Thurso . . 



. 3003 



N. 



3 



Wick . . 



. 30-03 



N. 



3 



Nairn . , 



. 30-07 



N.E. 



3 



Aberdeen . 



. 29-97 



N.N.W. 



6 



Shields . . 



. 29-98 



N.E. 



5 



Scarborough 



. 29-93 



N. 



5 



Yarmouth . 



. 29-87 



N.N.W. 



4 



Brussels . , 



. 29-79 



N.N.W. 



4 



Eighth zone below the crest. S.W. wave. 

 Helder .... 29*79 ? S. 2 



The regular decrements of pressure in each zone are in accord- 9 

 ance with the anterior slope of a N.W. wave, the crest of which 

 was not far from Valencia^ Greencastle, and Nairn. 



Table II. — Distribution of Pressure and Wind over the North- 

 west of Europe on April 20_, 1872, exhibiting a diminution of 

 pressure and consequent production of the posterior slope of 

 a S.W. wave. 



Zone on S.W. next above trough o/S,W. wave. 



Barom. Direction. Force. 



Valencia . . 29' 59-0-59 W. +7 



Corunna , . 29-67-0-I0 N. +9 



Trough o/S.W. wave. 



Roche's Point. 29-46-0-57 *N.N.E. 4 



Biarritz . . 29-40-0-27 Calm. 



First zone above trough. S.W. wave, posterior slope. 



Scilly . . . 29-64-0-34 *S.S.W. -3 

 L'Orient . . 29-68-0-19 S.E. -2 



Rochefort . . 29-54-0-23 N.E. 5 



Second zone above trough. S.W. wave, posterior slope. 



Greencastle . 29-53-0-56 ^E.. +5 



Pembroke . . 29-62-0-41 *S. 3 



Plymouth , . 29-67-0-.29 E.S.E. 1 



Third zone above trough. S.W. ivave, posterior slope. 

 Holyhead . . 29-62-0-41 *S.S.E. -3 



* The winds marked (*) thus are cyclonic. 



