ON THE METEOROLOGY OF PORT LOUIS. 



139 



Table XXIII. — Showing the Mean Height of the Barometer (corrected and 

 reduced to 32°) for each Month and Year, as derived from Six-hourly 

 Observations taken daily from 1860 to 1866, both inclusive. 



"While Tables XIII. and XVIII. show a decreasing vapour-J)ressure and 

 humidity, Table XXIII. shows an increasing atmospheric pressure. Hence 

 the gaseous pressure has also been increasing. 



The gradual diminution both of the vapoui'-pressure and humidity may 

 be due to the clearings which have been extensively carried on in the interior 

 of the island diuing the last fifteen or twenty years. It would be easy to 

 attribute the change to some general cause affecting the surrounding ocean, 

 but there seems to be no necessity for having recom-se to that supposition 

 •when we know that forests must act as preservers of moisture, and that the 

 forests of Mauritius have been rapidly disappearing. If observations had 

 been taken at localities where forests existed, before and after they were cut 

 down, the change would doubtless be much more marked than at Port 

 Louis. 



As to an increase of the atmospheric and gaseous pressures, -with a de- 

 crease of vapour-pressure, that is in accordance with a general law. 



The foUo-sving are the means of the atmospheric and dry pressures for con- 

 secutive periods of two years each : — 



Years Atmospheric 



Pressure. 



1860-61 30-036 . 



1862-63 30-042 . 



1864-65 



Bty 



Pressure* 



29-369 



29-385 



30-077 29-428 



These results are no doubt partly due to the disturbing action of hurri- 

 canes. 



l2 



