some cases be auxiliary. Pholas has been actually observed to use the shell as a filing or rasping instrument. A French naturalist1 proved that the valves were hard enough to bore the rocks in which the animal is found, and that in gneiss the marks of wear on the teeth were greater than in specimens found in shale. He also succeeded in getting Pholas to bore gneiss in captivity. The recent investigations conducted by Miss B. Lindsay 2 at the Gatty Marine Laboratory, St. Andrews, support this view. The details of the process were observed. Miss Lindsay states that in Pholas the method of working is double-it sucks and scrapes; and the process may be described as a combination of a nutmeggrater and a vacuum-cleaner. On one occasion the shell-scraping activity was actually made audible. The wall of a burrow in shale had been partly destroyed, with the result that the animal came in contact with the concrete floor of the tank in which the experiments and observations were being conducted. "The sound continued for hours on several successive days, and much resembled the gnawing of a mouse in wood." It may be mentioned that the shells of Pholas are composed of aragonite -a substance which is harder than calcite.

The habit of boring is common to the whole tribe of the Pholadidae. The principal rock-boring species found in British seas are as follows:

Pholas dactylus, the "piddock," is the largest British species, the shell sometimes attaining to 5 or 6 inches in length and 11⁄2 inches in breadth. On the south coast of England it is found at places in profusion near low-water mark; it occurs also on the west coast of England and Wales and on the Irish coast. Though rare in Scotland, specimens are recorded from the Firths of Forth and Clyde. The tubes of this form reach 8, 10, or even 12 inches in depth. At Tenby, in South Wales, as many as 100 specimens have been taken from 9 square feet of rock.

Pholas crispata has a wide distribution around Britain, but relatively is less abundant in the south of England than it is farther north. The largest examples exceed 3 inches in length by 14 inches in breadth. It makes burrows up to 3 or 4 inches in depth. This is the species which is the most important in numbers and activity at St. Andrews, its work being especially effective about and below low-water mark.

Pholas candida occurs all round the coast. The shell measurements rarely exceed 2 inches by of an inch. At St. Andrews it is scarcer than the previous form, thriving apparently below low-water. During blasting operations, carried on in 1896 in connection with drainage works, fine examples of this form were thrown up on the beach from depths below low-water mark.

Pholas parva is a smaller form, as its name suggests, the size of the shell being seldom more than 14 inches by an inch. It has been noted only along the south coast of England, the Bristol Channel, and the west shore of the Irish Sea.

Another member of the tribe, Pholadidea papyracea, is met with at very low tides embedded in rock on the coast of Devon, and again on the Irish coast. It is a small form and very fragile.

The bathymetrical range of the Pholadidae is from between tides to a depth of 25 to 30 fathoms.

Next in importance come the Saxicavae,1 which, although sometimes found free, usually make habitations in rocks. Occasionally they thrust themselves into ready-made crevices or utilise old burrows of Pholas, but generally they bore for themselves in calcareous rocks, less frequently in sandstone and shale. The species most active in our seas is Saxicava rugosa. The shell of this form may attain a length of an inch and a

breadth of half an inch. Borings are said to have been observed to a depth of about 6 inches. Wherever chalk or limestone occur on the sea coast the surface of the rock is apt to be riddled by Saxicavae (Fig. 3). The action of a solvent is usually invoked to explain the perforations, but, though occurring mainly in calcareous rocks, its bores are also found in other rocks; for instance, Miss Lindsay states that at St. Andrews it sometimes burrows in sandstone. There is some difficulty in crediting Saxicavae with mechanical means of boring, as the shells, in contrast with those of Pholas, are smooth and fragile, and unarmed with spines. Miss Lindsay states that the boring movements do not seem to be definite in direction and purpose, like those of Pholas, and concludes that the creature is comparatively little specialised for this kind of work. Many of the burrows are parallel to the surface of the stone, so that the animal lies on its side. It is possible that the work may be done by rasping either with silicious particles contained in the anterior part of the mantle (the existence of which is uncertain) or more probably by gritty particles of external origin.

Saxicava is found all round the coast of Britain, and its habitat extends from above low-water mark to a depth of over 30 fathoms. Mr. Peach1 (the father of Dr. Peach) obtained living forms from perforations in a rock specimen obtained from a depth of 30 fathoms, four or five miles off the Deadman, in Cornwall.

A closely allied form is Gastrochaena, a borer showing a preference for calcareous rocks, but which has been found also in decomposed granite. It is not common, though prolific at some parts of the southwest coast of England and the west coast of Ireland. Off Torbay, in Devon, at a depth of 10 fathoms, masses of limestone have been taken honey-combed by its excavations.

A rarer form, belonging to the same family as those just mentioned, Petricola lithophaga, though abundant on the opposite coast of France, has rarely been met with on our shores. Hitherto it has been noted only in the Bristol Channel and the south of Ireland.

Some Echinoderms form hemispherical cavities in rocks. As long ago as 1825, the surface of a fragment of rock from the coast of Clare 2 was described as being marked by depressions occupied by sea-urchins, and apparently formed by them. The cavities generally corresponded in size and shape with the stage of growth of their respective inhabitants. On that coast thousands of similar cavities in close juxtaposition, and many still occupied by the sea-urchins, were observed on ledges of rock about low-water mark. Occurrences of a like nature were noted off the coast of County Cork. Subsequently excavations made in rocks by sea-urchins have been recorded in Donegal Bay, and in many other parts of the world. Some of the most striking cases occur in the nummulitic limestone at Biarritz. Fischer counted from twenty to a hundred on the floor of troughs measuring 10 cm. deep and 1 square metre in extent. The holes themselves were 2 to 4 cm. in diameter. Another observer, Marcou, 5 in the same region found sea-urchins embedded in their excavations on the walls of pot-holes, the holes being arranged in stories one above the other. Some of these pot-holes were peculiar in that they possessed a central column of rock on the sides of which sea-urchins were also embedded. In some cases the central column, or style, had broken off at the base, appearing as a loose fragment somewhat larger than other stones found at the bottom of the pot-hole. It is inferred that the formation of these peculiar pot-holes is to be attributed partly to the action of the sea-urchins.

The boring due to these animals is not confined to limestones; cases are recorded in sandstone, gneiss, granite, and lavas.1 Off the coast of Ireland the only excavating species hitherto noted appears to be Strongylocentrotus lividus ; other forms, such as Echinus miliaris, have been noted elsewhere. It seems clear that the habit is not confined to any single species, and the recent observations of Fewkes reveal the curious fact that the same species does not resort to this practice in all the localities in which it is found. "The habit of excavating seems to be one which is limited to individual sea-urchins which live in certain exposed positions, where the tides are very high."2 This appears to show that the conditions favourable for the work of excavation are environmental or physical.

Many theories have been propounded to explain how the seaurchins make their hollows. The teeth of these animals are very hard, and the muscles which move their jaws are strong, and so many authorities ascribe the excavations to the gnawing and chiselling action of the teeth. But the depressions are so perfectly smooth and symmetrical that it is thought that the spines covering the test may do a part of the work by a rotatory motion of the sea-urchin, combined with motions of the animal produced by waves and tides. These hollows may serve primarily for protection, and partly also to ensure an adequate amount of water for the animal when the tide retires.

Observations are lacking as to the operations of sea-urchins on the coast of Great Britain. The fact that they are active on certain parts of the coast of Ireland, and on the coast of Brittany should induce naturalists to be on the look-out for evidence of their operations in other parts of the British Isles.

According to M'Intosh certain forms allied to the Polyzoa perforate calcareous rocks, but data as to their relative importance are wanting.

The total effect of the ceaseless boring of rocks at many localities by some or all of these various types of organisms must be very considerable. The sea, especially during storms, will complete the work of destruction, liberating young forms and larvæ to begin their operations over again on fresh sites. When the element of time is duly given its place as a factor we must recognise the importance of this work in the erosion of the sea-bed.

TRAVEL MEMORIES.4

By Lieut.-Colonel A. C. YATE, F.R.G.S., F.R. Hist. Soc.

(With Illustrations.)

LOOKING back from the autumn of 1917 upon the night of 7th June 1881 spent at Dehbid, I found my thoughts straying away to "memories" of Sir Charles M'Gregor, to whom I owed, I believe, my year with the

Afghan Boundary Commission, of Sir Robert Murdoch Smith, to whom I owed my introduction to the Royal Scottish Geographical Society and kindly hospitality at Teheran in 1881, and in Edinburgh and at Granton a decade or so later, and of our hosts at Dehbid and Abadeh in June 1881, Sergeants Hamilton and Hockey of the Royal Engineers. There are few living now who have any personal knowledge of the initial stages (1862-5) of the Indo-European Telegraph line, when it was laid from Baghdad to Teheran and from Teheran to Bushire. The proposed wire and cable route from Baghdad via Fao and Gwadur to Karachi was found so insecure owing to the malpractices of the Arabs, that this detour by Teheran was adopted as the lesser evil. Telegraphic communication from Europe vid Constantinople with Baghdad was, such as it was, the best method then available. When the present war broke out, three telegraph lines-the Indo-European, Turkish, and Eastern-connected Europe with the East. Practically, on 4th August 1914, the two first were closed to Great Britain. Of the men who made the Indo-European, Patrick Stewart, Goldsmid, Bateman-Champain, Murdoch Smith, St. John, Wells-all, I think, Royal Engineers-have passed away. Some idea of the lives they led and the obstruction with which they contended may be gained from Mr. Dickson's excellent Life of Major-General Sir Robert Murdoch Smith. It is with pleasure that I look upon the kindly, shrewd, intellectual face of the portrait that forms the frontispiece of this book. The last time I saw him face to face was in 1895, when he very kindly took me and my wife round the Persian art treasures of the Chambers Street Museum in Edinburgh. I am not aware of any one to whom the museums and art collections of the British Isles are so indebted for specimens of the arts of Persia as to General Murdoch Smith; and my own interest in the Hospitallers of Rhodes and Budrum drew me long ago to study the records of his excavations at Halicarnassus. When we were his guests in 1881 at Teheran, Captain Wells was his assistant, and, succeeding him as Director there, died comparatively young. Lieutenant St. John of the sixties was translated from telegraphy to frontier politics, and as residentat Kandahar in 1880-81 was a prominent figure. His small, active, wiry frame looked equal to any climatic vicissitude, and yet suddenly, to my regret, when he was acting for Sir Robert Sandeman as Agent to the Governor-General for Baluchistan, pneumonia carried him off.

Telegraph work in Persia in the sixties to eighties of the last century was no child's-play, and to its hardships our hosts, Sergeants Hockey and Hamilton, succumbed. Non-commissioned officers of the Royal Engineers who, as bachelors, came out to the Persian Telegraphs, frequently found comfort in conjugal union with Armenian women. Of Sergeants Hockey and Hamilton, one who knew them well writes: "They were the two most powerful men (ordinary human beings) that I have ever seen. Hamilton could, and has, knocked down a mule with a blow from his fist. He could lift the 'top' of a strainer (iron) pole, one in each hand, straight off the ground, and carry them above his head. They weigh about a hundred and twenty pounds each.