174' MARINE BAROMETER. 



Observations My observations upon the north coast of Australia are but 



and inferences little satisfactory, both because the changes in the barometer 

 to ascertain ihe ,, . , i • i i i . i-.^i 



correspondent were very small in so low a latitude, and tliat very little more 



changes of than the shores of the gulph of Carpentaria could be exa- 

 ^e", to bJex- ""'"^^ ^" account of the decayed state of the Investigator, 

 pected after which obliged me to return with all practicable expedition to 

 mar"ne baro-^ ^^""^ Jackson. An abridged statement, however, of the gene- 

 meter, ral height of the mercury under the five following circum- 

 stances, will afford some light upon the subject, and perhaps 

 not be uninteresting, 1 st. On the east side of the gulph, and 

 at the head, with the south-east monsoon, or trade wind. 2d. 

 At the head of the gulph with the north-west monsoon. 3d. 

 On the west side during the north-west monsoon, 4th. At 

 Cape Arnhem under the same circumstance; and 5th. In the 

 passage from Cape Arnhem, at a distance from the coast, to 

 Timor, with variable winds. 



In a memoir written by Alexander Dalrymple, Esq. 

 F. R, S. respecting the Investigator's voyage, there is this ge- 

 neral remark : — " Within the tropics, the monsoon blowing on 

 " the coast produces rainy weather, and when blowing from 

 *' over the land, it produces land and sea breezes." This I 

 found verified on the east side of the gulph of Carpentaria, be- 

 tween November 3 and 16, which time was employed in its 

 , examination ; for though we had found the south-east trade to 

 blow constantly on the east side of Cape York just before, and 

 doubtless it did so then, yet in the gulph we had a tolerably 

 regular sea breeze, which set in from the westward at eleven 

 or twelve o'clock, and continued till seven, eight, or nine in the 

 evening Towards the head of the gulph, the trade wind, 

 which blew at night and in the morning, came more from the 

 NE, and the sea breezes more from north and NW, but 

 without producing any regular alteration in the height of the 

 mercury, whose average standard was 29,95 ; it never fell be- 

 low 29,90 or rose above 30,04. At the head, ihe height of 

 the mercury remained nearly the same, until the north-west 

 monsoon began to blow steadily, about the iOth of December, 

 two or three days excepted, when the day winds were from 

 the south-eastward, and the mercury then stood between 

 29,80 and 29,85. At these times, however, there was usually 

 some thunder and lightning about, signs of the approaching 



rainy 



