ON THE NORTH-WEST COAST OF AUSTRALIA.
The great extent of the North-West coast of Australia, lying as it does between the parallels of 12 and 22 degrees of south latitude, no doubt subjects it to a variety of winds and weather, that is not experienced on the north coast; although, on that part of it north of the parallel of 15 degrees, there is probably much similarity.
As I cannot speak with certainty of the winds and weather that prevail on this extent of coast, at all seasons of the year, the following remarks will be confined to such portions of it as were visited by the Beagle, and will apply only to the particular seasons in which she was employed there.
To the eastward of the meridian of 123 degrees east longitude, and at a short distance from the land, the east and west monsoons will be found regular; but the easterly monsoon is very light to the southward of 13 degrees latitude.
Between Clarence Straits and Cambridge Gulf, and during the months of September, October, November, and December, the wind during the day is a seabreeze between North-West and West. In September, and until the middle of October, we found the wind as follows: About sunrise, a light breeze sprang up from South-East or East which gradually drew to the northward towards the middle of the day, in the afternoon, a seabreeze from North-West or west, becoming light towards sunset, but freshening again soon after that, and blowing a moderate and pleasant breeze between North-West and South-West all night.
During the latter part of the period (November and December) the winds were more constantly from the West or West-North-West, blowing from that quarter throughout the twenty-four hours, but much more moderate at night than during the day; at full and change of the moon, the breezes were much stronger than at other times, and upon one or two occasions, at the time of the moon's quartering, there was a light breeze from South-East in the morning.
During the month of November, the ship was at anchor, twelve miles within the entrance to Victoria River, and sixty-five from Point Pearce, on the sea coast. For the first three weeks of this time, the seabreeze was regular from North-West or West-North-West, generally setting in about noon, and lasting the greater part of the night; in the mornings, and until noon, it was mostly calm, or very light winds from the northward. In the last week of this month the weather was very unsettled and squally, with much thunder and lightning, and rain, the wind mostly between South-East and North-East; after which, the westerly breezes set in again, and continued until we left the coast in the middle of December.
During the whole of this period the westerly winds did not appear to come from any distance, but to be merely local seabreezes, as they did not cause any sea upon the coast, nor did they reach far in shore; as we frequently observed smoke at no great distance from the coast, rising perpendicularly, or influenced by a light south-easterly wind, and this at times when the seabreeze was strong. From this it would appear, that the westerly monsoon had not reached so far to the southward, nor did we find, after sailing from Point Pearce, that the winds were at all steady from the westward, until we had reached to the northward of Cape Londonderry, which is in latitude 13 degrees 45 minutes South. To the northward of this, the winds were from the westward, accompanied by fine weather during the day to the southward of that point--sometimes as far as South-West--and at night inclining to the northward of west, but generally speaking, we found the wind to the southward of west, and the current running from half a mile to a mile an hour to the North or North-North-East.
The currents between New Holland and Timor, are said to run to the westward, during the easterly monsoon--and in the opposite direction with the westerly; but they seem to be influenced by every trifling change of wind--as on the 20th, 21st, 22nd, and 23rd of December (when the westerly monsoon might be supposed at its height) we experienced light, variable winds, between South-East and East-North-East--during which period the current ran to the westward--at times, a knot an hour. We were then between the parallels of 11 1/2 and 13 degrees, south of which we experienced winds between South-South-West and West until we were to the southward of the North-West Cape, when they became more southerly, and at times South-South-East (in January). Throughout all this period, the weather was fine, and different from what was expected during the westerly monsoon.
All that part of the North-West coast of New Holland, between the North-West Cape, and Cape Londonderry, appears to be very much subjected to light winds, particularly during the easterly monsoon, the strength of which is not felt to the southward of 13 or 14 degrees of south latitude. During the westerly monsoon, strong winds and gales from the North-West at times blow upon the coast, but they do not appear to be frequent. The strongest winds at this season, are the heavy squalls between East-South-East and North-East (and which may with propriety be termed hurricane squalls); fortunately they are not of long duration, rarely lasting over two hours. They give ample warning of their approach, by the gathering of a heavy bank of clouds between North-East and South-East, and much lightning in that quarter. Appearances such as these frequently precede the squall some days, but coming gradually nearer (to the westward). The barometer shows no indication of approaching bad weather, being only acted upon by the immediate change; these squalls mostly occur in the night, or between sunset and sunrise.
During the latter part of the westerly monsoon, on that part of the coast between Cape Villaret and Point Swan, we found the weather remarkably fine, with the exception of an occasional short, but severe squall, from the eastward. During the day there was generally a moderate seabreeze between North-West and South-West commencing in the forenoon, and lasting sometimes nearly until midnight--on which occasions it blew strongest during the night); during the other part of the twenty-four hours the wind was light from the eastward or calm. Captain King experienced similar weather in August.
It was not until we had reached Point Swan, in latitude 16 degrees 20 minutes South that we experienced any of the bad weather that is usually met with, at this season of the year, a few degrees to the northward; it commenced in the last week of January, and continued until the middle of February, during which period, there were some strong gales from the westward, between North-West and South-West accompanied by heavy rain, thunder and lightning; but although there was a good deal of dirty weather, it was by no means constant, as there were occasional intervals of fine weather, with moderate westerly winds. This was the only bad weather on this part of the coast, during the season, that could be said to be caused by the westerly monsoon, if we except the East-South-East squalls, that do not occur in the easterly monsoon.
While this weather lasted, the easterly squalls were quite suspended, and the heavy bank of clouds that had generally been noticed in the South-East had dispersed for the time; but after the strong westerly winds had ceased, the weather was generally fine, and the wind mostly from some western point; there were occasional showers, and the clouds in the eastern horizon resumed their threatening appearance, bringing some hard squalls, and rain from that quarter. In the middle of March (being the time when equinoctial gales are looked for in most parts of the world) there were two or three days of squally, unsettled weather, with rain, that seemed to terminate the season of the westerly monsoon. After the 1st of April, the weather was invariably fine, and the easterly squalls had ceased to trouble us; land and seabreezes became regular, and the easterly monsoon had no doubt set in to the northward; the strongest breezes now were from South-East but, generally speaking, the winds were very light near the land.
It does not appear that the westerly monsoon blows with any degree of regularity, to the southward of the 13th degree of south latitude; although for some degrees south of that, the weather is influenced by it, and winds between West-North-West and South-West will be experienced, and from the appearances on many parts of the coast, there are no doubt strong gales at times from the westward, that send in a very heavy sea. During the easterly monsoon, the weather is fine on the North-West coast, particularly in the months of May, June, July, and August; this is undoubtedly the best time for visiting it; land and seabreezes are regular, and the temperature is very agreeable.
The average range of the thermometer on that part of the coast, between the North-West Cape, and the meridian of 120 degrees east longitude, during the above-mentioned period, was between 75 degrees in the middle of the day, and 60 degrees at night, on board the ship, and the general course of the wind as follows, viz.
About sunrise, or sometimes a little before that, a breeze springs up between South and South-South-East and draws to the eastward as the sun rises, rapidly increasing in strength, and between 8 and 11 A.M. often blows a fiery breeze; towards noon it moderates, and rarely lasts until 2 P.M., after which there is a light breeze from North-East which at times reaches to north; the nights are mostly calm, or a light breeze from the south-westward; at the full and change of the moon, we found the south-easterly winds stronger than at other times; dews at times very copious.
All this part of the coast is subject to the effects of mirage, by which its outline is at times very much distorted, but generally speaking it ceases with the strength of the breeze, and as the sun attains a little altitude. When the effects of mirage was observed in the morning, I noticed that the winds were much lighter throughout the day, than usual.
During this part of the year, the atmosphere is clear, with a cloudless sky, and the coast is exempted from the violent East-South-East squalls, that are of frequent occurrence, while the sun is in the southern hemisphere, and the land consequently very much heated.
Towards the latter end of August, and in September, the winds are not quite so regular, and there are occasional intervals of two or three days of westerly winds.
That part of the North-West coast between the North-West Cape, and the 116th degree of east longitude, seems to be subject to westerly winds at all times of the year. The prevailing southerly winds that blow along the west coast, appear to draw round the Cape, and follow the direction of the land. Between April and October (when the easterly monsoon is blowing to the northward) they are generally to the southward of west, or between that point and South-West, but during the westerly monsoon between West and North-West.
Upon getting to the westward of the North-West Cape, the wind becomes more southerly, and draws to the eastward of south as the distance from the land increases, and will be found varying between South-South-East and East-South-East, generally speaking as far south as the parallel of 30 degrees of south latitude, after which it is mostly to the westward of south, so that ships making a passage to the southward, along the west coast of New Holland, will rarely be able to make any easting, before reaching that latitude, particularly during the summer months. In the winter a ship may occasionally make a quick passage to the southward, if happening to be upon the coast during a northerly gale; and as all these gales are preceded by North-East winds, a sufficient offing may be gained to enable her to run on, when the wind gets to the southward of west.