RAIN-MAKING

New Zealand Mail, Issue 9, 1 November 1907, Page 41

RAIN-MAKING

OFFICIAL REPORT

When the North Otago district a month or two ago was in the throes of a drought the conditions became so

strained for the farmers that a suggestion that experiments should he resorted to with a view to inducing rain was somewhat eagerly entertained. The Government, which had extended considerable assistance to the droughtstricken farmers of the district, sympathised with the movement, and without committing itself to any opinion as to the prospects of success, despatched the Rev. I). C. Bates, F.R.G.S., F.IL Met. Hoc., Government Meteorologist, to watch the experiments and report on the results.

Mr Bates’s report, which reached the Government sometime ago, contains some interesting passages with relation to the experiments.

PRE VIOUS DROTJGTITS. The Oamaru district, which is dependent on the easterly winds for its rains, has suffered prolonged drought periods in former years, notably in 1889, 1890-1, and 1897-8. 5 The period of deficient rainfall which led to the experiments extended from January, 1906, to August, 1907, the rainfall for the eighteen months being 45 per cent, less than the stun of the average falls for the eighteen months included. The average annual fall for Oam aim for a period of forty years was 21.87 inches, the maximum being 32.82 in 1870, and the minimum 13.47 in 1881. COMPARING THE PERIOD.

The following tables show the difference between the drought period under discussion and the averages for the district for the forty-year period referred to : MONTHLY FALL.

In only one month of the drought period, December, 1906, did the total fall exceed the average, and then the difference was merely 16 points. The number of days on which rain fell in the drought period compare as follows with the averages:— Average Drought period

The records kept at the Kauroo Hill station, oue of the centres of the drought in the rural district, differed considerably. As to the effect of the drought, Mr Bates writes:—

The results, though not comparable with the effects of droughts I have experienced in Australia, were more severe than I had imagined possible in this country. . . x only saw one small field of fair sized turnips in the district, while on the average fifty to sixty truckloads were being brought from Southland every day for Northern ami Central Otago. . . Stacks of straw were commanding high prices, and quite 9300 tons of fodder had to

be imported by the settlers to keep their stock alive.

Much stock, the report continues, liad to be removed elsewhere, and the fact that there were so few dead animals in the fields were attributed largely to the timely and generous assistance afforded t.y tue uovernnient in the matter of transport of fodder. The yields of wheat were the lowest since 1897-6, and the yield of oats was the lowest on record. It was only 2u bushels, as against 41 the previous year, and 21.7 in the drought period of 1897-8.

THE EXPERIMENTS. The promoters of the experiments to try and induce rain were men who- commanded t-lie respect and sympathy of the public, and a large sum of money was readily subscribed for the purpose. This was supplemented by the Government, which supplied explosives at cost price. Mr Bates was ordered to proceed to Oamaru to watch the experiments, and he was careful on arrival there to disclaim any responsibility for them. The idea in the minds of those who were conducting them was io cause passing clouds to precipitate their moisture, and Mr Bates was asked to advise as to the particular times when the air would be saturated and favourable for the experiments. “Though 1 could not share their very sanguine hopes,” he writes, “I tried my best to meet their views, and to the utmost of my abilities heartily co-operat-ed with their committee.” The probability of rain with certain disturbances rarely amounts to absolute certainty. “Events were moving in such a manner,” the report continues, “that I could forecast a period of saturation in the near future. The times that are most favourable for rain, fortunately for the district, coincided very nearly with such widespread and abundant rainfalls as had not occurred for years, and on this account, unfortunately for myself, the task of giving conclusive evidence as to cause and effect in the experiments was thereby rendered more dinicult. While admitting this, 1 desire most clearly to maintain that in no case was I able to trace such effect or success in rainmaking as due to the explosions as some of the local residents claimed at the time with considerable assurance.”

LOCUS OF THE EXPERIMENTS. The experiments were carried out at Raki’s Table, 1059 ft above sea level, ana fourteen miles from Oamaru; and at Round Hill Totara, 500 ft above the sea and six miles from Oamaru. When the first experiments were carried out on the 16th August, at Raki’s Table, the conditions were regarded as fairly favourable. Three shots were fired, the last and most powerful being 40lb of dynamite and 251 bof powder. Only natural changes were observed to be going on in the atmosphere, though a slight shower was reported not far distant. As a result of these trials, it was decided to give the explosions more resistance, by making the charges stronger and- firing them from rocks. Mr Bates himself expressed the opinion that it would be move efficacious to use small cannon with charges of powder than to use the explosives mentioned above, which were enclosed in kegs or cases. Cannon had been used in other places, but more for the purpose of preventing hail, or precipitating rain before its formation.

THE SECOND EXPLOSIONS. On the 18th August rain had fallen in a number of places, but none at Raki’s Table, so the committee decided to have some explosions there. The explosions were heavy, and there was some rain in different localities, but Mr Bates writes:

I regarded these as perfectly natural, and was confirmed in my opinion when I learned that the rain squalls had the same intermittent character long before they reached us. It could hardly be maintained that the explosions would have so marked an effect as this on the rain fourteen miles away, and against the sweep of a wind at the Table averaging about twentyfive miles an hour. While I saw no perceptible difference made in the showers sweeping down upon us and

progressing over the country, others were qrrite as decided in their opinion that the rain thickened heavily after each successive shot. The barometer continued to rise, and those who watched the instrument agreed that there was no fall after the successive shots.

The strongest of these explosions was produced by 501 b of guncotton and 10-0 of dynamite. Rain continued on the 19th and 90th, but Mr Bates considered the widespread and heavy rains could hardly be attributed to the artificial means adopted.

THIRD SERIES. On the 22nd August there was a trial on a larger scale. The barometer was falling rapidly, and there were indications of lam before long. Charges varying up to 2001 b were discharged from Raki’s Table, but, as far as was. apparent to Mr Bates, there was no change. Though the mist was heavy, the rain was not quite ready, and the explosions did not seem to expedite it. It did, however, fall some hours afterwards, and some people in the locality might have attributed it to the explosions, but ho believed nobody who was actually on the spot could entertain such an idea. The artificial el]ores were puny in comparison with the mighty forces which were at that moment developing independently over thousands of square miles in a cyclone similar to, but more intense than, that which had approached only a few days before. The dry period was at an end. “ I watched carefully,” says the report in a summary note, " but the explosions had apparently no more effect on the air than would the striking of a match in a room.”

The forces arrayed against artificial changes in the atmosphere are tremendous —almost beyond conception. . . . An inch of rain corresponds to 22,635 gallons, or lOf tons Bqr 261 b of water to the acre, or over 64,640 tons to the square mile. The iatent heat developed or relaxed under such conditions of condensation from vapour to water for an inch oi rain-to tliesouaio mile is estimated as equivalent to the work done by 100,060,000 horse-power ior half an hour. Consider, again, the sweep of a wind, five hundred miles across and three miles high, blowing for an hour at the rate- of twenty miles. The force of the mightiest explosion, with all its gas put forth into the air is, in comparison, less than a drop in a bucket. Until it can be shown that the temperature of the air can be controlled by gigantic cooling operations, we may look in vain for any alteration in the natural and weilestablished order of events by way of production of artificial rain.” BENEFIT OF FORESTRY.

By way of recommendation, Mr Bates advises the judicious planting of trees in the districts likely to be affected by the drought. The settlers, he says, have planted a great number of pines which have nourished well, but if larger and more varied plantations were made, particularly in belts intercepting the north-west and eouth-west winds, though they might not increase the rainfall, they would not only act as shelters and wind-breaks, but they would also conserve the rainfall which now occasionally runs off in floods, and the planting of deeper rooting trees would bring up water from the lower tables and prevent surface evaporation by the wind. So far as can be gathered, the only objection to this would bo the danger of harbouring small birds, but the losses in this direction would undoubtedly be more than compensated.

Average 1996. 1907. Inches. Inches. Inches January 2.24 — .43 February 1.88 1.25 1.39 March ... 1.32 .52 1.41 April ... 1.73 1.16 .58 May 1.62 .73 .71 June 1.78 1.42 .24 July ... 1.67 .59 .56 August 1.47 .59 — September 1.89 1.46 — October 1.55 .62 — November 1.98 .95 — December 2.302.46 —

January days. 12. 1906. 1907. 5 February 11.6 13 9 March 9.7 10 11 April 9.0 5 7 May 8.0 4 2 June 7.4 5 4 July 8.0 6 7 August 8.0 4 — September ... 9.0 8 — October 10.0 7 — November 11.0 5 — Beeember 13.0 10 —