Book Title: Indian Antiquary Vol 58
Author(s): Richard Carnac Temple, Charles E A W Oldham, S Krishnaswami Aiyangar, Devadatta Ramkrishna Bhandarka
Publisher: Swati Publications
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AUaust, 1929) REMARKS ON THE ANDAMAN ISLANDERS AND THEIR COUNTRY
Calm weather can be counted on in February to April and in October. Fous and chilly night winds are common in January to March in the valleys andinner harbours and also after excessive rains. Off-shore breezes at night and on-shore breezes in the day are most marked during calm weather, due to the differences in temperature of sea and land. March and April are often hazy. The barometer normally varies but little between 29.8739 and 29-722° Fahr., being highest in February and lowest in June.
The temperature is highest in March, April and May, and lowest in December, January and February. It may be said to rain all the year rouni; that is, always in most months of the year, sometimes during every month, and on an average overy other day of the year, which is to say that there are on an average 188 days in the year on which some rain falls. The dricet months are January, February and March and the wettest July, August and September, but very heavy rain may fall in May and June. As much as 25 to 10 inches of rain may fall in a month, and in the 'wet' parts of the Islands much more.
This climate is, however, really due to the facts that the Andamans are situated between 10 and 14 degrecs North in the open sca (Bay of Bengal), and are therefore subject to both the South-West and North-East Monsoons (really tho W. S. W. and N. N. E.). Thø former blows during May, June, July, August, and September (5 months) and the latter during November, December, January, February and March (5 months), the inonths of chango being April and October.
A tidal observatory with self-registering gauge was established on Ross Island (Port Blair Harbour) in 1890 (lat. 11° 41' N.: long. 22° 45' E.), which gives a mean range of yreatest ordinary spring tides of 6.6 ft. The highest high-water and the lowest low-water are 8.0 ft, above and 0.8 ft. below datum lovel (Indian low spring water-mark, at Port Blair 3.53 ft. below mean sea level.) The apparent time of high water at the full and change of moon is 9 h. 36 m. At various parts of the great harbour of Port Blair the actual times for the tides depend on wind, strength of current and distance from the open sca. The average variation in timo of high tides at the several points is from 18 m. to 57 m, later than at Ross Island, and in height it is from 20 inches less to 17 inches more than at Ross. Wind and current will at these points effect time by as much as 29 m. either way. No doubt the same thing happens in the many other harbours and creeks in these mountainous islands, a fact of much consequence in cvery-day life, where communications are maintained along the shores by boat.
(III) GEOLOGY. There has been no complete geological survey of the Andamans, but expeditions by experts have been officially undertaken to make preliminary examinations of the Islands. These examinations have been carried on under the greatest difficulties of every kind, not the least being the dense and lofty forests with which the entire Islands are covored. Judging by the report of such cxpeditions, the submarine ridges forming them contain inuch that is geologically characteristic of the Arakan Yomas and formations common also to the Nicobars, to the islands off Sumatra and to Sumatra itsell. The older rocks characteristic also in the vame form of the Nias Islands on the West Coast of Sumatra aro probably early tertiary or possibly lato cretaceous, but there are no fossils to indicate age. The newer rocks common to the Nicobars and Sumatra are in Ritchio's Archipelago chiefly and contain radiolarians and foraminifera. There is coral along the coasts everywhere and the Sentinel Islands are composed of the newer rocks with a superstructure of coral, but no atoll is known in thc vicinity of the Islands. There is a good dcal of serpentine rock, also somo jasper, chromite, and copper and iron pyrites, and small pockets of coal. About Port Blair a firm grey sandstone identifiable with the Negrais rocks occurs with interbedded slaty shales, and not infrequently nests of coaly matter and occasionally of conglomerate and pale grey limestones. This
