26 THE ROYAL SOCIETY OF CANADA 
167 years before, or an average wearing back of almost exactly a foot 
in a year. Robson’s Map, however, does not quite agree with the 
description which he gives of the site of York Factory, for while the 
former shows it only about 100 feet back from the river, the latter 
states that it was ‘‘about eighty yards from Hayes river.” Now 
Robson was a builder, and as his published plan of Fort Prince of 
Wales on Churchill river has been found to be correct his plan of 
York is likely to have also been correct, though he may not have been 
quite so particular to mark its exact distance from the river bank. 
It is probable that his plan is more correct than his description, but 
if the latter is correct the bank has been worn back at the rate of 
1 foot 10 inches a year during the above period. 
It is interesting to note, too, that the deepest water just within 
the mouths of these two rivers is near the west bank which is being 
cut away, and it would seem probable that the deep channel is moving 
westward with the wearing back of the cliff which overlooks it. 
From the facts and considerations above enumerated we can 
readily see why there are no natural harbors on the south coast of 
Hudson Bay. A gently sloping sea floor, in which there were no 
troughs or indentations, gradually rose from beneath the water; 
the streams draining the advancing land cut channels into it, but 
they scarcely reached the sea, and did not extend out under it; and 
the westward transgression of the mouths of the present rivers pre- 
vents the formations of even such channels as the water would cut 
if it were confined within narrow limits. 
Churchill harbor is an example of what the water will do in 
making a channel even below sea level if it is not allowed to spread 
out. The harbour is a rock-bound basin which was filled with till 
or boulder clay up to the general level of the surrounding till covered 
plain. An interval of 1,100 feet between the rocks allowed the stream 
to flow from, and the tide to ebb and flow from and into the basin, 
and the till has now been scored out of this rock-bound interval 
or channel to a depth of 120 feet, while at the same time the ebbing 
tide has carried away the till and formed a fairly deep basin half a 
mile in diameter just within the rocky neck or mouth of the harbour. 
Possibly a little assistance with explosives applied to the till that re- 
mains within the rock-bound basin might enable the water. that rushes 
out between the rocks at the entrance of the harbour with the ebbing 
tide to greatly enlarge the extent of the deep water. 
But there are no hard rocks to confine the waters at the mouths 
of the other rivers, and they spread out and clear a very wide instead 
of a deep channel. 
