THE SPRING SEASON

New Zealand Herald, Volume LXXII, Issue 22224, 26 September 1935, Page 14

THE SPRING SEASON

DATE OF COMMENCEMENT

ASTRONOMICAL DEFINITION \ . . ■■ - PERIODS OF THE YEAR Professor S. E. Lamb, of the School of Engineering, Auckland University College, writes us follows: "An item of news appearing in the Herald states that September 24 marks the astronomical beginning of spring. Previously the writer of these notices had used the title 'official' for the dates ho had assigned as the commencement of the seasons. This was a vague title, of no significance, but it was misleading to the reader in that it conveyed a fictitious importance to the date. Now, however,4 the word astronomical has been substituted for official, and thereby a mistake has been made, because from an astronomical point of view there can bo no misconception about the seasons of the year. "The period of the year when the days and nights are of equal length marks ail equinox, and is midway between the summer and winter solstices, which occur on December 22 and Juno 22 respectively. The solstices mark tho astronomical mid-summer and mid-win-ter. Therefore, midway between these dates must be the astronomical middle of spring or autumn. Hence, September 22 is the astronomical middle of spring, and not the beginning." Crux Australis replies as follows: — In describing September 24 as the first day of the astronomical spring season the Herald was following the practice of many of the leading almanacs, in which the date of the vernal equinox is followed by tho explanatory words:"Spring commences." The seasons are so clearly defined in astronomical text-books that there can bo no misconception. For instance, the Astronomer Royal, Dr. Spencer Jones, in General Astronomy, published last year, says: "The ecliptic is divided into four equal parts by the two equinoctial and the two solstitial points and the periods taken by the sun in apparently traversing from one of these points to the next are called the seasons." _ From the astronomical point of pew summer began on December 23 last, Autumn on March 22, Winter on June 22 and Spring on-September 24. Many factors influence the actual meteorological seasons, such as the nature and amount of the soil, the wind directions, etc., but, considering the whole of the southern hemisphere, it can be said that the coldest days occur in August and the warmest in February. The meteorological seasons therefore can be regarded as commencing in the same months as the astronomical seasons, but several weeks earlier than the latter, as was explained in the Hkrald article. With regard to Professor Lamb's other point, the word "official" has more meanings than the one most commonly applied, and was used in the sense "properly authorised," as the seasons undoubtedly are by astronomical and calendar usage. When it was found that the meaning was being misunderstood in some quarters the word "astronomical" was substituted.