Page:Cyclopedia of Western Australia, volume 1.pdf/31

plays may be referred to the combined operation of different causes, which are reducible chiefly to these four—distance from the Equator, height above the sea, distance from the sea, and prevailing winds, which may thus be regarded as forming the great bases of the law of climate. The history of meteorology in Australia may be said to have been inaugurated by the late Sir George Kingston in South Australia in the year 1839. Systematic rainfall observations were continued by this gentleman till 1878, the last 18 years being concurrent with more systematic and complete observations at the Adelaide Observatory.

At Perth no official records of rainfall were taken till 1875, when the observations were commenced at the Government Gardens by the Surveyor-General (Sir Malcolm Fraser), and where they are still continued.

Western Australia covers a vast area of 975,920 miles, and if we extend a line from Albany in the south, latitude 35° 2', to Wyndham in the north, latitude 15° 27', it will be at once seen what a great diversity of climate the largest of the six States of the Commonwealth possesses. In dealing with the climatic conditions of the State the Editor wishes to express his obligations to the State Government Astronomer, Mr. W. E. Cooke, M.A., F.R.A.S., for most of the information contained in this article.

During the first half of last century meteorological observations were confined largely to rainfall only. Systematic observations of pressure, temperature, rainfall, wind, and other meteorological elements began with the foundation of the astronomical observatories in the capitals of the different States. The Perth Observatory owes its birth to the foresight of the Forrest Government in 1896. Sir John Forrest laying the foundation-stone of the principal building. Among the many great observatories of the world few can surpass it for beauty of position or perfectness of equipment.

In taking up the subject of the State's climate generally it will be best to divide it roughly into three parts—(1) The climate of Perth and the south-west and south coastal districts; (2) the climate within the Tropics; and (3) the climate of the interior.

The first division may for practical purposes be considered as bounded by the coastline and also by a straight line drawn from Eucla to Geraldton, but if for the sake of expediency we are to take Perth as representing the whole, certain exceptions will have to be made.

The rainfall is heaviest in the extreme south-west, diminishing thence both northward and eastward. It also falls off from the coast and coastal ranges in all directions inland. Between Bunbury and Albany the summer temperature is considerably cooler than elsewhere. The sea breeze which compensates so much for the oppressive heat of summer in the coastal districts does not reach far inland. With these exceptions we can regard the climate of Perth as typical of our first climatic division and proceed to discuss it.

"Just as there are two distinct types of weather," Mr. Cooke remarks, "so there are two distinct seasons—winter and summer." The former sets in, as a rule, rather abruptly. From May to the end of October may be considered the winter months, and the weather during that period is dominated by the passage of the "highs" and "lows." The average rainfall for each month is as follows:—

These figures might convey the impression that Perth is a very wet place during the winter, but the reverse is the fact.

Owing to the tendency for the rain to fall principally in heavy showers and at night, and to the sandy nature of the soil which rapidly absorbs it, the general impression of the Perth winter is that of a succession of fine, bright, calm days, varied occasionally by a severe but brief storm. The weather is, on the whole, delightful, but it may perhaps be too mild. One misses the keen frosty feeling that is experienced in other places, and its absence probably justifies to some extent the popular statement that the climate is enervating.

At night it is frequently cold, July showing an average of five nights during which the minimum thermometer in the screen registers below 40°. (As this description or Perth is to be taken as representing more or less the whole of the South-West district, it must be stated that severe frosts are by no means uncommon inland. The coldest parts of the State at night are Southern Cross and Katanning, and here the thermometer frequently falls below 32°, especially if exposed to radiation. The mean minimum in the Stevenson screen for July is 38.7° at Southern Cross and 40° at Katanning.)

Very severe floods have been occasionally experienced at Perth and elsewhere in the past, but for a long time there has been an almost entire absence of these; in fact, during all the years that systematic records have now been kept no great floods have occurred.

The summer does not set in quite so abruptly as the winter. With an occasional hot day in October it commences generally in November, but does not as a