214 REPORT ON THE SURFACE DRIFT OF THE ENGLISH CHANNEL 



21st), was recovered at Portscatho also on the 25th. The two bottles 

 were recovered by diil'ereut individuals at different times of the day. 

 We may assume, therefore, that they had not lain long on the shore 

 before being picked up. 



The force of the wind was taken to be the mean of the forces recorded 

 at Prawle I'oint, Plymouth, and Falmouth. The records for Prawle 

 Point and Plymouth are expressed in terms of the Beaufort scale, the 

 former being extracted from the Daily Weather lieports of the Meteoro- 

 logical Ollice, and the latter being supplied to me by the Borough 

 Meteorologist at Plymouth, The Falmouth records are the readings of 

 the automatic anemograph at the Falmouth Observatory, and are 

 expressed in units of velocity (miles per hour). To compare these 

 records I have employed Scott's table of the velocity-equivalents of the 

 various figures of the Beaufort scale. The recorded direction of the 

 wind during the period was approximately the same at all three stations, 

 i.e., about E.N.E., but the records of the force of the wind showed more 

 discrepancy than might have been expected. At Prawle Point the force 

 varied between 5 and 7 throughout the period, the average being 6 ; at 

 Plymouth it was more variable, and the average was 4; while at 

 Falmouth the resultant average velocity compiled from the 73 hourly 

 records during the period only amounted to 13'9 miles per hour, which 

 is equivalent to a force intermediate between 2 and 3 on the Beaufort 

 scale, but much nearer 2 than 3. It is reasonable to expect that the 

 force of an E.N.E. wind blowing over the southern part of our islands 

 should be weaker at Plymouth than at Prawle Point, owing to the 

 retarding effects of greater friction, for such a wind at Prawle Point 

 would come to an observer there direct from the sea (Lyme Bay), while 

 at Plymouth it would be distinctly a land breeze. But it is ditUcult to 

 understand the low readings of the anemograph at Falmouth during this 

 period, especially as there was no corresponding reduction in the force 

 of the wind further westward, the force at Scilly being recorded in the 

 Daily Weather Pieports as varying between 4 and 6, the average being 

 5. The error introduced by the employment of a table of velocity- 

 equivalents of the Beaufort forces no doubt partly accounts for the lack 

 of correspondence between the data, and the records at Prawle Point 

 were possibly in this case slightly in excess of the actual velocities ; but 

 there is still a residuum of error which must apparently be attributed to 

 the effects of local environment upon the velocity of the wind recorded 

 at the Falmouth Observatory. 



However, by taking the mean of the observations at Prawle, Plymouth, 

 and Falmouth we shall probably eliminate the errors of observation and 

 measurement, and obtain a fairly true measure of the force of the winds 

 over the sea in this district for the period in question. The resultant 



