to south of the Peninsula is 20 miles, and its greatest length from east to west 30 miles.

The wells of Jaffna are subject to certain peculiarities. Their general level appears to be affected by the state of the tides, not however to such an extent as to cause a diurnal action. It is however a well known fact that during the north-east monsoon the wells of the district rise to their greatest height, and that height diminishes as the force of the monsoon decreases. The large mass of water in the Bay of Bengal affected by this monsoon causes the level of the Jaffna lake to be affected to the extent of 18 inches increase of tide, at the same time that the above-mentioned rise in the wells occurs. Another fact is, that cultivators in digging irrigation wells are obliged to observe the greatest possible caution, as after passing a certain depth the water becomes brackish, and this peculiarity exists throughout the Peninsula. Again it is equally curious to observe how closely fresh and salt water flow together without amalgamating. Whilst building a causeway at Vannatipalam across the salt inlet, in this Poottoor district, the foundations were laid in salt water, but close to this and in the centre of the inlet fresh water could be obtained in several places and in large quantities, although during freshes those spots are covered with 3 or 4 feet of salt water. These facts may prove of interest and of some use in considering any theory which may be based upon the results of the experiments, hereafter to be narrated.

The Poottoor well itself is a large rectangular pit in the limestone rock, and its dimensions are about 40 feet in length by 25 in width. A slope down to the water level has been made, as is common to all the artificial tanks of Ceylon and India. Tradition connects it with some springs on the Coast near Tondamanaar, but it is only tradition as it would be simply impossible to trace the course or source of any springs in so level a country. The only previous experiments made were in 1824, when engines of considerable power were employed, to raise water from the well, with a view of irrigating the district. The only result obtained however was the

establishment of the fact that it was impossible to affect the level of the well or to check the curious rise and fall of its water. This latter phenomenon has earned for it the title of the "Tidal Well of Poottoor."

I think I have now mentioned all the facts I am aware of, which might assist any one in forming an opinion as to the cause of the peculiarities of this well. These peculiarities are three in number.

First in importance is the tide above mentioned.

Secondly, the presence of salt water from a depth of between 45 and 50 feet to the bottom of the well, &c.

Thirdly, its apparent inexhaustibility. The experiments just completed were undertaken with reference to the two first conditions only, the experiments of 1324 being considered conclusive as to the third.

EXPERIMENTS.

The first step taken was, by a careful section taken from the low water mark on the southern to the low water mark on the northern shore, to ascertain the relation that the level of the surface water of the well bore to the tidal marks of the sea on both shores. Levels were taken for a distance of 17 miles from Jaffna on the south coast to Valvetty torre on the northern coast.

The fact so established is, that the level of the fresh water in the well coincides almost exactly with the low water level of the sea on both coasts.

The next experiment was conducted with a view of ascertaining at what depths the fresh water ceased and salt water commenced, and to procure specimens of the water at various depths to be sent to England for analysis. An instrument with a closely fitting valve was made for this purpose, so arranged that the valve could be opened and closed again at any given depth.

The first symptom of brackishness was found between 40 and 50 ft. down, and it appears certain that it is at this point that the salt water enters. Specimens of the water at the surface, 45 ft., 95 ft., 145 ft. (the bottom) were procured and put into sealed bottles.

The water from the bottom when first brought up, smelt strongly of sulphureted hydrogen.

The surface of the fresh water is 14 feet below the ground line, and the total depth of the well varies between 140 and 145 feet. Dr. Ferguson of the Army Medical Staff kindly assisted me in making these experiments.

It being desirable to ascertain how far the tide in the well coincided with that of the sea on both coasts, Dr. Ferguson and myself at the well and two assistants at Jaffna and Valvettytorre respectively, took notes at every half hour from 6 A. M., till 6 P. M. The following is a tabular statement shewing the rise and fall of the tide observed at all three places in inches.

Time.

Jaffna Lake. Well at Poottoor.
Well at Poottoor. Valvettytorre.

By the foregoing table it will be observed that the well alternated 3 times during the day, whilst the sea was not affected to a similar extent.-The well also rose whilst the sea fell, and this part alone destroys all hypotheses that I have as yet heard discussed. The subject therefore remains in an unexplained state and offers a field for scientific enquiry and discussion.

On the air breathing Fish of Ceylon-By The REVD.

PRINCIPAL BOAKE.

Having been recently induced to make some experiments on the respiration of certain species of fish, in order to ascertain the correctness of a statement of mine which had been communicated to Professor Huxley by Sir Emerson Tennent, I am under the impression that an account of those experiments with a description of the habits of the fish in question, will come within the scope of the Asiatic Society's operations, and may perhaps be deemed by the Committee to possess sufficient interest to entitle a paper on the subject to admission into its Journal.

During my residence in England in 1855-1856, I became acquainted with the facilities which recent discoveries, or, to speak more accurately, the ingenious application of old discoveries to the construction and management of aquaria had afforded to those who wished to observe the habits and natural history of the various tribes of aquatic animals. Knowing that very little attention had been paid to that branch of natural history in Ceylon, I lost no time, on my return to the Island, in establishing a fresh water aquarium; and, in watching the proceedings of its inhabitants, my attention was very soon attracted to a peculiar habit which some of them had, of ascending at nearly regular intervals to the surface, so as to bring the mouth for an instant in contact with the air. That habit is particularly conspicuous in the fry of two species, viz., the Loolla and the Maddecariya, which speedily cover the surface of the water in which they are confined, with small bubbles of air or gas. I noticed also that the species of fish, to which that habit belonged, were much less sensitive to any impurity in the water in which they were confined than were those which did not pay periodic visits to the surface. Had I been a practised natura