434 REPORT—1883. 
series of stations across the ice at the Montanvert gave, in 1842, the following 
(simultaneous) relative velocities :— 
1:000 1:332 1:556 1-367. 
The same points being recovered in 1844, the relative motions were (by a single 
observation of the space moved over in five days) :— 
1-000 1:339 1:362 1574; 
ratios almost the same, but slightly increasing, which corresponds with the fact 
mentioned above (3), that when the absolute velocities are greater the relative 
velocities are so too, which was here the case, for the velocity denoted by 1-000 
was a little greater in the second case than in the first.’ 
Professor Tyndall, who in many ways extended Forbes’s observations, has such 
faith in the regularity of that motion that in all his researches he assumes it as an 
invariable fact which does not require any further testing, for, according to the 
published accounts, the daily motion seems, with one exception, to be always 
obtained from a single set of measurements. But Tyndall also noted a sudden 
motion of a few inches at one place; and if such sudden disturbances do take 
place, it is evidently better to obtain the average daily motion from observations 
taken as close together as possible, as only then would these sudden slips be 
eliminated. 
The author’s observations are not favourable to great regularity of glacier- 
motion, but in bringing them forward he is well aware of the great evidence on 
the other side, and he therefore gives them only as an example that great irregu- 
larities may occasionally take place. 
He gives in a table the average hourly motion in centimetres in the different 
stakes between July 2], 24, and 25 respectively :— 
Hourly Motion in Centimetres. 
Stake: I. Il. TUTE) pe lIVe ast Ve Vi... | VEL. VET. 
Between July 21, 3 P.M., and : , : : , ze . : 
July 24,1 PM. hg he usa aL 1-4 aka 13 13 1:2 06 
Between July 24, 1 P.M, and f d 2 y : : ~ ~ 
July 25, 8 AM. Olu sb. 1:6 2:5 2°2 1:9 4-1 Bb 
Total average between J wy | 
21, 3P.M., and July 25, 11 
8 A.M. ‘ J 
Digit 1-4 1-4 15 1-4 1:8 16 
The first stake was placed about 70 metres from the western end of the glacier, 
the successive distances to the other stakes being in metres 47, 53, 26, 29, 48, 47, 
‘92. The last stake was just within the eastern moraine. 
A glance at the table will show that the glacier-motion during the first three 
days of observation was much less rapid than during the last, and this is especially 
striking on the eastern side, where the last stake had actually moved during the 
last nineteen hours two anda half times further than during the previous seventy 
hours, the hourly motion being nine times as large in the second period. The 
relative motion between the eastern and western ends was preserved during the 
‘time over which the observation extended. At first it was the western end which 
moved more quickly, but during the last days the eastern end followed so rapidly 
si the total average for the four days shows a greater movement of the eastern 
side. 
It is needful to add a word as to the accuracy of these numbers, as the author 
would not wish to press them against the much more extended series of measure- 
ments given by Forbes and Tyndall, unless he felt pretty sure that they fairly well 
presented the actual motion of the glacier during the period of observation. He 
may say at once that he does not pretend to rival the accuracy of former observers. 
His instrument was only divided to minutes, but the errors of setting were much 
smaller, and half-minutes could easily be estimated. Nevertheless he will assume 
that an error of one minute has actually been made; this would imply an error of 
cabout 5 centimetres for the first stake and less than 15 for the last. In the most 
