22— SUNRISE AND GROWTH. 



By Colonel H. E. Rawson, C.B., R.E., F.R.Met.Soc, &c. 



Fellow of the Physical Society. 



Experiments to ascertain whether there is any special growth at 

 sunrise are lacking, and such a book as Osterhout's Exferiments with 

 Plants, igo$, does not suggest making any, either in connection with 

 temperature or light effects upon plants. The following were carried 

 out during February, March, and April, 1906, in a garden in 

 Pretoria, Lat. 25° 45 S and Long. 28° 14 E, at a height of 4450 feet 

 above the sea, and 270 miles from it. The mean temperature varied 

 from 70° F in February to 62° F in April ; the mean maxima were 

 82° F and 79° F for the same months respectively, and the mean 

 minima 59° F and 47° F. The rainfall was 4.2 7ins. during 

 February, 3.o5ins. during March, and o.52in. on 2 days during 

 April. Cloudy days were few, and during the important tests, from 

 March 23rd to April 23rd, the sky was overcast at sunrise on only 

 two, and on one of these there were occasional gleams of sun. On 

 21 days the sky was cloudless as regards these experiments, on 5 it 

 was overcast some time during the day, and on 6 there were detached 

 clouds. A Rambler Rose grew 33 inches in 3 weeks and 19 inches in 

 the two following weeks during the period of the experiments. 



That some connection would be found between sunrise rays and 

 growth was suggested by a wonderful cloud-phenomenon, which was 

 seen at that hour on March 12th, 1905, from the deck of 5.5. Gaika, 

 when in Lat. 8° S and Long. 3° W, close to the Magnetic 

 Equator. As the sun rose out of the water due E at 6 a.m., the 

 sky was suddenly covered with myriads of cirrus threads as fine as 

 those of a cobweb, and each one stretching continuously from true 

 north to true south parallel to one another, and without break or 

 irregularity of any kind. By the sun's action each particle of frozen 

 moisture in the cirrus levels had been symmetrically brought into 

 lines, so as to form a series of arches at right angles to the rays of 

 light, At a higher level than tlie cirrus lines there were a few flecks 

 of cirrus cloud drifting from north to south, but the lines had a 

 movement of their own. As measurements with instruments proved, 

 they swung slowly round as if endeavouring to keep themselves 

 perpendicular to the sun. At noon the lines had thickened consider- 

 ably, and half-an-hour before sunset there was a double set of them, 

 one perpendicular, and the other parallel, to the incident rays. They 

 were watched during the process of forming, and appeared to be 

 evolved out of minute globules of cirrus haze. By no possibility 

 could this have been the effect of wind, and it was the opinion of 

 those who were taking the measurements that the arrangement of 

 the globules into lines was directly due to the sun's rays. 



This wonderful phenomenon was repeated on two consecutive 

 days and was carefully studied in all its details, to see if it would 

 throw any light on analogous cases in which a symmetrical 

 arrangement of particles of matter takes place under the action of 

 incident rays. In botany we have such a disposition of chlorophyll- 

 granules on cell-walls which are perpendicular or parallel to the rays. 



