At the spot where the temperature of the water was the highest, that is, in what are termed the _Caldi_, or hot baths, a considerable quantity of a substance is ejected, which produces a deposit of a brownish-yellow colour. Having collected a quantity of this deposit, he ascertained it to consist of oxide of iron and silica, in the proportion of about four parts of the former to three of the latter; and although the iron, at the time of its deposition, proved to be a _peroxide_, he thinks it probable that it existed in the water in the state of _protoxide_. He also supposes, that the oxide of iron and the silica had been dissolved together in the water, and been deposited from it in combination. He conceives that the fact which he had some years before noticed, of the analogy between the base of silica, and that of boracic acid, together with those observed by Berzelius, furnish sufficient reasons for classing silica amongst the acids, and for rendering it probable, that the oxide of iron and silica undergo a real chemical combination in the warm water, and that they are separated from the latter in consequence of the reduction of its temperature, after it has issued from the mountain. A small portion of oxide of iron, he observes, is found in the waters of Bath, in which case it is also accompanied by silica; and he believes that, in many other instances, the oxide of iron is dissolved in water through the same agency: he moreover regards such facts as throwing considerable light upon the manner in which ochre is generated. Sir Humphry Davy returned to England in 1820; and, on the 19th of June, in the same year, his venerable friend Sir Joseph Banks, who, notwithstanding his increasing infirmities, had continued to discharge the duties of President of the Royal Society to the latest period of his life, expired at his villa at Spring Grove, at the advanced age of seventy-seven. Discussions necessarily arose as to the appointment of a proper successor, when persons of high and even exalted rank were proposed as candidates; but the more influential members of the Society at once found, in their own Council-chamber, two philosophers, whom they considered equally entitled to the honour of the situation, and equally well calculated for the discharge of its duties--Sir Humphry Davy, and Dr. Wollaston; but the latter having signified his fixed determination to decline competition, gave the whole weight of his influence to the former; and, under that arrangement, he received from the Council the compliment of being placed in the chair, until the general election of officers at the ensuing anniversary. As the period of election approached, a few Fellows of the Society attempted to raise a clamour in favour of some more aristocratic candidate. To this circumstance, Davy alludes in the following letter. TO THOMAS POOLE, ESQ. Grosvenor Street, June 1820. MY DEAR POOLE,