516 
Proceedings of the Royal Society 
that my measurement of the depth of the funnel is 3 or 4 feet 
in excess of Bunsen’s. 
In devising the apparatus employed I was kindly assisted by 
my friend Professor Fuller of Aberdeen. I procured from Casella 
of London a self-registering maximum thermometer, which is now 
on the table. We had made for it a case of brass, the ends of 
which were made to unscrew, and were pierced with holes. The 
thermometer was kept in its place in this case by little wedges of 
cork, which, however, allowed the water to have free passage through 
the tube from end to end. To protect the thermometer and case 
against injury from the sides of the G-eysir-funnel, we slid over its 
ends two large pieces of cork, and connected these lengthwise with 
slips of wood. This arrangement was found to answer admirably, 
unless that the large masses of cork required so heavy a weight 
to submerge the whole apparatus that we had some trouble in 
hauling it in towards the side when each reading was taken. We 
had also omitted' to provide swivels to prevent twisting of the cord 
when the cap was unscrewed, and from this cause much time was 
lost in getting each successive reading. The following 12 were all 
that Mr MacCarthy and I could obtain, though we worked well 
all the time we were there, unless for 6 or 7 hours when we went 
to rest in the boer or farm-house near by, leaving a watch, with 
orders that we should be called if any unmistakable signs of an 
approaching eruption were given. From this division of our time 
it resulted that of these 12 readings, one-half were taken on the 
evening of the 6th August, and the rest on the morning of the 7th. 
Allowance must be made for this, in accordance with one of Bunsen’s 
results as to the general rise of temperature in the whole column 
as a great eruption is coming on. 
Temperature-measurements at the G-reat Greysir, 6th and 7th 
August 1874. 
Depth in feet 
Observed temp. 
Calculated 
Diffs. 
from surface. 
Fahrenheit. 
boiling-point. 
0 
187° 
210° 
23° 
10J 
190° 
224°-3 
34°-3 
18 
197° 
233° 
36 
27 
211° 
241°-8 
30 o, 8 
