
307 
REcoRDS OF SUNSHINE. 
Since May Ista daily record of the amount of sunshine received 
at the station has been kept by means of a sunshine recorder 
imported for this purpose. This instrument, manufactured by 
Negretti & Zambra, consists of a glass sphere which, acting as a 
burning glass, is made to produce a charred line upon a strip of pre- 
pared paper, suitably placed in the focus of the sun’s rays. ‘The 
paper is divided by lines at a distance apart representing hours, so 
that one may see at a glance the time of day, and the duration of 
any sunshine that may occur, This instrument fails to make any 
record for a considerable time after sunrise, and for about the same 
time before sunset, also whenever the atmosphere issmoky or shghtly 
hazy, although the sun may not be obscured. This effect amounts 
to from 10—15 per cent. of the total sunshine. 
In connection with the above, a record has been kept with an 
instrument constructed essentially upon the plan given in Nature, 
vol. 31, page 319. This consists of a silvered globe placed before a 
camera with a short focused lens, with the axis of the instrument 
placed parallel to the axis of the earth. In this position the sun’s 
rays, reflected from the surface of the globe, form an image of the 
sun on a piece of sensitive paper in the camera. In consequence of 
the rotation of the earth, this image will describe the arc of a circle 
corresponding in length to the duration of the sunshine. By means 
of a circle divided into 24 parts, to represent hours, the amount of 
sunshine for any day isreadily determined. 
Instead of using the silvered globe, our instrument has been con- 
structed by placing a small camera in the axis of the first mentioned 
instrument, so that the glass globe which forms its lens serves as a 
reflector for the latter. This has the advantage of making the 
results obtained by the two methods comparable, as they are always 
exposed to the same amount of sunshine. 
The last described instrument is much more sensitive than the 
first, having shown throughout the season about 10 per cent. more 
sunshine than the first. This however, like the first, fails to make 
a record for a short time after sunrise and before sunset, but for a 
much shorter time. The sensitive paper used in the instrument is 
the same as is used by photographers for silver prints, and is well 
fitted for this purpose; but a more sensitive paper would no doubt 
give a record earlier in the morning and later in the evening. 
The difference between the results obtained in these two Ways gives 
some indication of the difference in intensity of the sunshine for 
different days. : 
In the tables given below appear the daily records for each instru- 
ment since May Ist. The record for each day is divided into four 
periods, the first including that part before 9 a. m., the next two 
being the three hour periods 9—12 and 12—3, and the last all after 
3 p.m. The number of hours between sunrise and sunset for each 
day is also given. The totals for all are carried out for each month 
together with percentages of total sunlight. The results are inter- 
esting, as they show the distribution and amount of sunshine 
throughout the season. 
It is hoped that the continuation of these records for several years, 
together with careful observations upon the growth of plants may 
show some relation between the amount of sunshine and plant 
development. 
