force originally impressed upon it, and to the degree of resistance offered by the varying thickness and solidity of the stratified rocks.

A letter from the Rev. Richard Hennah, jun., dated Jan. 19, 1815, was read.

The object of this letter is to state that, in addition to the information contained in the former letters of this gentleman, (read Nov. 18, 1814,) concerning the occurrence of organic remains in the Plymouth lime-stone, he has recently found many well-defined shells of the genus turbo, and of other genera, at the east end of the Hoe under the citadel; and also fragments of shells in a quarry at Cat-down.

A memoir on the native oxide of uranium of Cornwall, by W. Phillips, Esq. M. G. S. was read.

Uranite in green tabular transparent crystals, imbedded in ferruginous quartz, has been found by Mr. Phillips, at Carharrock, near St. Die. It has also been found by him in very minute crystals, varying in form and colour, and accompanied by pitch blende, at Tincroft mine near Redruth; also in well defined crystals, and accompanied by pitch blende, at Tol Carne mine.

At Huel Jewel this mineral occurs on red copper ore; and in a single instance has been found on the surface of Wavellite from Stenna gwyn near St. Austle. Specimens of extraordinary beauty have been discovered within the last three or four years at Gannis lake copper mine near Callington, on decomposed granite.

The larger crystals of this mineral are all deeply striated; and even the most minute ores, although seemingly well defined, are not capable of being accurately measured by the reflecting goniometer. From some very satisfactory clearages which Mr. Phillips has obtained, it appears to have natural joints parallel to the lateral faces, and to the two diagonals of a tetrahedral prism.

The paper concludes with a description, illustrated by drawings, of 46 varieties of crystalline form.

A paper, entitled Supplementary Observations on Quartz Rocks, made in 1814, by Dr. Macculloch, was read.

This rock forms the larger portion of the great valley of the Tunnel, where it alternates with micaceous and with argillaceous schist, with lime-stone, and with porphyry. It may be observed passing insensibly into granite, and, when it alternates with micaslate, the proportion of quartz rock will be found to prevail in the vicinity of granite; and that of mica-slate at a distance from the granite. In Ben Gloe it occurs incurvated and contorted; and on Cairn Gower are some beds consisting wholly of large and small rounded pebbles. In Mar forest it alternates with large incomplete garnets. In Glen Tilt it presents a finely laminated structure, like the schistose sand-stones of the coal strata, and is divided by natural joints into rhomboidal tables. In Ben Gloe it occurs of a beautiful pink colour; and in Glen Fernat it is mixed with scales of mica forming an avanturine capable of receiving a good polish.

March 3.-The reading of Mr. Horner's paper on the Geology of the South Western part of Somersetshire was begun.

ARTICLE XII.

SCIENTIFIC INTELLIGENCE; AND NOTICES OF SUBJECTS
CONNECTED WITH SCIENCE.

I. Lectures.

Middlesex Hospital.-Dr. Merriman's next Course of Lectures on Midwifery and the Diseases of Women and Children will be delivered at the above hospital during the months of April and May. The Introductory Lecture will be read on Monday, April 10, at half-past ten o'clock.

II. Smithson Tennant, Esq.

It is with much concern that we announce the death of Smithson Tennant, Esq. F. R. S. and Professor of Chemistry in the University of Cambridge; a man in whom genius, talents, and virtue, were united in their highest forms. Although his industry was checked by a frame naturally weak, and a languid state of health, his acquirements in science were remarkably general, and in many branches profound.

The circumstances of Mr. Tennant's death were most afflicting. He was returning from France, where he had been several months, and was waiting at Boulogne for a favourable wind. He had actually embarked on Wednesday the 22d of February, but the vessel was obliged to put back; and it was determined, if the weather should be tolerable, to make another trial in the evening. During the interval Mr. T. proposed to a German officer of distinction, whom he had accidentally joined on the road, and who was also going to England, to ride with him to Buonaparte's Pillar, near Boulogne. In returning he deviated a little to look at a fortification near the road. But as they were attempting to pass a draw-bridge, which, owing to some neglect, was not properly secured, the bridge gave way, and they were precipitated into the trench. The officer fortunately escaped without any serious hurt; but Mr. Tennant was found fallen under his horse, and was taken up speechless, his skull and one of his arms being considerably fractured. He was conveyed with difficulty to the hospital at Boulogne, as the nearest and most convenient place to receive him, and expired in half an hour. His remains were interred at Boulogne. A fuller account of this interesting philosopher is preparing, and will be given in an early number of the Annals.

III. Dr. Seetzen, the German Traveller.

Dr. Seetzen is little known in this country, except through a translation, by the Palestine Society, of a brief account by him of the countries adjoining the lake Tiberias, the Jordan, and the Dead Sea. As his merits are very extraordinary, it will be interesting to give a short sketch respecting him.

Ulrich Jasper Seetzen, born in the Russian lordship of Jever, is the son of an affluent farmer. He was educated at Gottingen,

where he took a degree in medicine; and having steadily regarded as the final end of his studies the exploring the interior of Africa, he prepared himself by the study of natural history in all its branches, Eastern languages, and astronomy, geography, &c. In 1802 he left Gotha, accompanied by a young man of the name of Jacobsen, and went to Vienna, whence he proceeded with some difficulty to Constantinople, where he arrived in December, 1802. Thence he went to Smyrna, which he quitted in October, 1803, having previously explored the adjacent country. He then resided at Aleppo, and afterwards at Damascus ; afterwards he examined the geological structure of the country towards Jerusalem, Lebanon, and Latitibanon. In 1805 be travelled through Arabia into Egypt, and finally arrived at Cairo. During residence at this last place (for two years) he transmitted his very valuable observations in separate dissertations to Germany, where many have been published, and many remain in the possession of his relations. In 1809 he quitted Cairo, returned into Arabia, and in Nov. 1810 he was at Mokka, since which no correct account of him has reached this country. A report has been received of his death, but in a very suspicious form. It would be gratifying to his friends to know his fate, as they would then be enabled to give the whole of his valuable researches to the world, a part of which only has hitherto appeared in the journal of his liberal friend Baron Von Zach.

IV. Gas Light.-Conveyance of Steam in Pipes.-Smallest Angle at which Objects are perceptible.

I have been much gratified by the information which has come out respecting the saccharometer, in consequence of my inquiry in your Annals. The " Philosophical Intelligence" is a most interesting part of that work.

Permit me to suggest to you that accidents, arising from philosophical negligence, if I may use the expression,-such as the late explosion of a brewer's store cask, and a recent accident with a gaslight apparatus at Birmingham,-deserve to be recorded in your Annals, for obvious reasons. Á friend of mine was going to light two large manufactories with coal gas, but since the late accident he has been undetermined whether to proceed or not. Will it be presuming too much to ask your opinion respecting the new mode of illumination with gas? The opinion of so experienced a chemist and philosopher would have a most beneficial influence. And what sort of coal is to be preferred for producing the gas in question? I presume the diameters of the conduit pipes have hitherto been taken. at random, and that the pressure on the reservoir of gas for sending a stream through the pipes has not yet been accurately observed, or at least not published.

I am also desirous to inquire how far steam has been known to be conveyed, or how far it probably can be conveyed, for heating water; and how large the conducting pipes should be to produce a required

effect. Is any damage to be expected from the sudden condensation of the steam on its first application to the cold water: I have been told that the pipes are liable to burst from this cause; a circumstance which I think Count Rumford never mentions in his essays on this subject.

One more query, and I have done. Has any experiment been published which ascertains the smallest object or angle that is perceptible to a sound unassisted eye, or an eye assisted with a given inagnifying power? In a philosophical work translated from the French I have read that the eye is incapable of perceiving an object which subtends an angle of less than half a minute of a degree. I remain, Sir, most respectfully, your obliged servant,

Feb. 3, 1815.

M.

V. Meteorological Table. From the Register kept at Kinfauns Castle, N. Britain. Supposed Lat. 56° 234. Above the Sea 129 feet.

No. 1. Ou a conical detached hill above the level of the sea 600 feet.... 33.84

The Royal Medical Society of Edinburgh having agreed to appoint a Committee for the purpose of receiving the communications of members, and of others through their medium, who may favour the Society with interesting facts and experiments in Medicine, or with unusual appearances in morbid dissection, beg leave earnestly to invite the members to transmit such communications to the Society as soon as possible.

The Committee, consisting of six extraordinary members resident in Edinburgh, together with the four Presidents ex officio, will proceed immediately to consider such papers as may be transmitted to them, with an ultimate view to publication.

You sometimes insert algebraical communications in your Annals of Philosophy. I have lately discovered that all numbers have four imaginary cube roots, which is contradictory to the generally accepted theory, that "every equation has as many roots as it has dimensions, and no more."

The imaginary cube roots of the number 64 are -2±√12; but the following quantity raised to the third power shows that it is also a cube root of the same number 64.

36 + 0 + ( − 2 + 6 √ − 3) √ − (1 − 3 √ − 3)

3)

3√ 3√

('3