70 
Proceedings of the Royal Society 
4. Note on Homocheiral and Heterocheiral Similarity. 
By Sir William Thomson. 
Monday, 3 d March 1873. 
The Hon. Lord N EAVES, Vice-President, in the Chair. 
The following Communications were read : — 
1. On the Mud Banks of Narrakal and Allippey, two 
Natural Harbours of Befuge on the Malabar Coast. By 
George Bobertson, Esq., C.E. 
In the course of an examination of the harbours and river 
mouths of India, which I have recently been making for the 
Government of that country, instructions were sent me to examine 
the backwater communication of the Malabar coast, with special 
reference to the possibility of taking advantage of the anchorage 
at such localities as Narrakal and Allippey, and opening out com- 
munications between them and the backwaters. As these anchor- 
ages are so remarkable, and the phenomena connected with them 
are probably known to but few members of this Society, and the 
places themselves perhaps never visited by any member present, 
I have thought a short account of these mud harbours of refuge 
would be of some interest. 
And, first, for a few words on the backwaters of Malabar. These 
consist of a network of lakes, river mouths, short rivers, and 
artificial cuts or canals, by which cargo boats can travel, with but 
one or two interruptions (now being overcome), from Buddagherry 
(to the north of Calicut), in lat. 11°*35, to Trevandrum, the capital 
of the state of Travancore, in lat. 8°*29. Eventually the system 
will be continued almost to Cape Comorin. The great value of 
this internal water communication is best shown in the south-west 
monsoon, when communication by sea is suspended for several 
months. 
The south-west monsoon, which commences early in June, is a 
great bugbear to the commerce of the west coast of India, partly 
