330 The American Geologist. December, i899 . 
resorted to, it would be easy to treat the forms in the way this 
kind of work has usually been done heretofore. 
The cusp which Prof. Tarr first describes — the recurved 
spit in Sidney harbor, which I take to be that locally called 
South bar, between the harbor and the South Arm — is hardly 
the best one for the case which he argues, on account of its 
position in a tidal estuary. By the process of map reading, it 
would undoubtedly be set down as due to violent tidal currents. 
But inquiry on the part of Prof. Tarr elicited the information 
that these currents are very feeble, and that no others of im- 
portance are known. There is little if any doubt here that 
wave action has been at least the dominant constructive force. 
Within the lakes themselves the conditions are yet more favor- 
able to wave work, as opposed to that of currents. 
Let us look at these conditions. The Bras d'Or lakes, as 
Prof. Tarr has stated in the paper referred to, are a series of 
northeast-southwest valleys, depressed sufficiently to afford 
the sea entrance at both ends. Thus salt and fresh water are 
mixed in their basins, with enough of the former to give a ma- 
rine aspect to the fauna and flora. There is therefore a theo- 
retical possibility of severe tidal action ; but considerable in- 
quiry on my own part and that of others has failed to discover 
this. In some places the rise is so small that, according to the 
inhabitants, although the water is salt there is no tide — which 
of course is not true. In others the rise amounts to about two 
feet. In no case, so far as I can ascertain, is there a tidal 
current of more than the weakest nature. I have satisfied my- 
self by study of the eel-grass that a very faint movement exists 
in some parts ; but it would be impotent to move more than 
the finest mud, and its power could be overcome by a slight 
breeze. 
At the time when the drowning of these valleys occurred, 
the topography was varied ; and as a result the margins of the 
lakes are sinuous, and a multitude of small and large hills now 
stand up as islands. The efifect of this diversity, exceedingly 
pleasing to the eye, is to give many bays, fjords, islands, and 
the dead-waters that accompany them. All these factors, es- 
pecially in the limited space occupied by the lakes, tend to give 
a maximum of shoreline for the area, hence greater oppor- 
tunity for coastal erosion. But, on the other hand, these very 
