59 
at the total solar Eclipse in 1882. 
the rays of the sun which were being collected and measured, and 
in order to protect the eyes from the intense glare of the sun it 
was prudent to use neutral tinted spectacles. The moment the 
temperature of the air passed upwards through the temperature 
of the skin was signalised by the spectacles feeling hot. Although 
the temperature rose to 105° F. the capacity for heat of the rim of 
a pair of spectacles is too insignificant to cause any inconvenience. 
i 
Discussion of Observations. 
The observations made with the Calorimeter on the 16th, 17th 
and 18th May are given in detail in Table III. and they are 
represented graphically in Fig. 8. On the 16th the distillate 
was received in a cylinder capable of holding over 100 c.c. and 
graduated into single cubic centimetres. In the two columns 
for rates on this day, the one is the rate per minute while 10 c.c. 
were collected, and the other the rate per minute while 20 c.c. 
were collected. On the 17th and 18th a tube graduated into half 
cubic centimetres and holding 20 c.c. was used. Time was taken 
as every 5 c.c. were collected, and the tube was emptied when 
20 c.c. had been collected. The readings for every 5 c.c. were 
made without removing the receiver from the distilling tube. 
The portion of 20 c.c. was measured in a truly vertical position 
and is more exact than the measurement of its constituent 
portions of 5 c.c., although every care was taken to note the 
time when exactly 5 c.c. had run without running the risk of 
losing any of the distillate. 
The most important manipulation is attending to the equatorial 
motion of the instrument. The observed rate of distillation agrees 
the more closely with the true rate the more carefully the axis of 
the instrument is kept pointed towards the sun. This was con- 
trolled by observing the shadow of the steam space on the top of 
the condenser with which it is concentric. 
The position was adjusted every two or three minutes when it 
was usually put a shade in advance of the true position so as 
to give it a position correct for the middle of the interval. 
The calorimeter ought always to be fed with pure distilled 
water. Unfortunately this was not available, and Nile water had 
to be used. It contains a considerable amount of earthy car- 
bonates and is apt, after prolonged use, to froth. With the glass 
dome, however, this was at once detected, and if it was serious the 
water was changed. 
