1879 -] Relations to that of the Glacial Epoch . 19 
I need hardly state, that no amount of pressure, however 
great, has the least tendency whatever to produce a melting 
of the ice by heat unless this pressure performs work, and 
the quantity of ice melted will then be not in proportion to 
the pressure, but to the work performed by the pressure. 
The pressure here referred to, which is supposed to produce 
the melting, is the weight of the ice, or, in other words, the 
force of gravity. 
When considering the amount of heat derived from work 
of compression it was proved that, in the case of the 
Antarctic ice-sheet, the total amount of work which can 
possibly be performed by gravity is determined by the thick- 
ness of the sheet. It was shown that if 1400 feet be the 
thickness of the sheet, 700 foot-pounds per pound of the 
sheet is the greatest amount of work that gravity can per- 
form. It follows therefore that, supposing the whole of the 
work is employed in heating the ice by compression and 
fridtion the heat thus generated would amount to only 0*9 of 
a thermal unit per pound of ice. It must be obvious that 
in the case of a flat and tolerably uniform sheet like the 
Antarctic, in which the pressure must of course be pretty 
evenly distributed, little or no melting can take place 
from this cause, as it requires not 0*9 of a thermal unit, but 
142 thermal units, to melt a pound of ice already at the 
melting-point. The total work of 158 pounds of ice would 
need to be concentrated upon 1 pound in order to melt it. But 
such an unequal distribution of force in a sheet so uniform 
is at least extremely improbable. The tabular form of the 
southern icebergs, with their stratification parallel to their 
upper surface, shows the flat character of the ground on 
which they have been formed. This circumstance appears 
to have particularly struck Sir Wyville Thomson, as well as 
all who have visited the Antardlic regions. “ The stratifi- 
cation,” says Sir Wyville, “ in all the icebergs which we saw 
was, I believe, originally horizontal and conformable, or very 
nearly so. I never saw a single instance of deviation from 
the horizontal and symmetrical stratification which could in 
any way be referred to original structure As I have 
already said,” he continues, “ there was not, so far as we 
could see, in any iceberg, the slightest trace of structure 
stamped upon the ice in passing down a valley, or during its 
progress over roches montonnees , or any other form of uneven 
land ; the only structure, except the parallel stratification, 
which we ever observed which could be regarded as bearing 
upon the mode of original formation of the ice-mass was an 
occasional local thinning out of some of the layers and 
• c 2 
