CAUSES OF GLACIER MOTION. 
41 
that it is open to the most serious kind of contamination, and 
to my certain knowledge it has at times received a considerable 
amount of sewage matter. The water from Thomas a Becket’s 
Well is distinctly deteriorated after the manuring of the 
gardens situated near it. 
In speaking thus of the Inferior Oolite springs I do not 
wish to underrate their value, but only to condemn that water 
which is obtained from them in and near the town, and even 
more so that which is obtained from them in some few 
villages where proper drainage works do not exist. # As a 
matter of fact, very large quantities of good water are obtained 
from this formation ; indeed, in some places in this and neigh¬ 
bouring counties it is the chief or only supply. Mr. De Bance 
says that “Unpolluted spring water from the Oolites is unsur¬ 
passed in its comparative freedom from all kinds of organic 
matter ; ” and “ They are bright, sparkling, and palatable, and 
excellent for all domestic purposes except washing, but the 
hardness is mostly temporary, and so capable of being 
removed by Clarke’s process/’ 
(To be continued.) 
ON THE CAUSES OF GLACIER MOTION.! 
BY W. P. MARSHALL, M.I.C.E. 
Glaciers have their origin in the snowfall above the line 
of perpetual snow. All the share of rain that is due to fall in 
the particular locality, instead of falling in a liquid state and 
at once passing away to the lower regions of the mountains 
and valleys as rivers, falls in a frozen state as snow, which 
remains where it falls, and accumulates in the higher regions 
of the mountains. At all places above the level where the 
annual snowfall exceeds the annual melting from the direct 
heat of the sun, combined with the evaporation from the 
surface, the mass of snow upon the mountain tops would 
receive a permanent addition every year, and the heights of 
the snow mountains would undergo continuous increase, 
rising higher and higher indefinitely if there were not some 
counteracting influence to prevent this rising. This counter¬ 
acting influence is the “ Glaciers,” which are in reality 
* One of tlxe worst waters I ever analysed came from a village 
where these remarks would apply. 
f Transactions of the Birmingham Natural History and Micro- 
scopical Society. November 23, 1886. 
