at the total solar Eclipse in 1882. 59 



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. 



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. 



