The effect of mechanical disturbance in determining saline crystallization, is illustrated by the symmetrical disposition of particles of dust and iron by electricity and magnetism. Strew these upon a plane, and present magnetic and electric forces at a certain distance from it; no effect will be produced. Communicate to the plane a vibratory movement; the particles at the instant of being liberated from the friction of the surface, will arrange themselves according to the laws of their respective magnetic or electric attractions. The water of solution in counteracting solidity, not only removes the particles to distances beyond the sphere of mutual attraction, but probably also inverts their attracting poles. Hence, when they are again brought within the attracting limit, by abstracting the water or the repulsive caloric, some additional force is necessary to revert this liquid arrangement of the poles. It is thus that a crystal, brought into contact with the surface of the solution, may be conceived to act.

Experiments 3d, 4th, and 5th, seem to prove that neither the chemical properties of the atmosphere, nor its pressure, have any influence on the crystallization.

ART. XV. Biographical Notice of the late Mr. CRANCH.

In the introduction to the Narrative of the Expedition to the Congo, biographical notices are given of several of the unfortunate persons who fell victims to the dreadful fever which terminated the hopes of the party: That of Mr. Cranch we think peculiarly interesting, and we present it to our readers.

MR. CRANCH was one of those extraordinary self-taught characters, to whom particular branches of Science are sometimes more indebted, than to the labours of those who have had the advantage of a regular education. He was born at Exeter in the year 1785, of humble, but respectable parents; at eight years of age he had the misfortune to lose his father;

and as the circumstances in which his mother was left, did not enable her to provide for all her children, John, the subject of the present memoir, was taken charge of by an uncle living at Kingsbridge. The main object in life, and which was nearest to the heart of his relation, was the accumulation of wealth; and his extreme penury denied to his nephew, almost the benefit of a common education. The miserable guinea which procured for him a year's instruction, was wrenched from him with so much grudging, and in a manner so unkind, as to be then severely felt, and never afterwards forgotten.

At the age of fourteen, this provident relation first put him out as an apprentice, to learn" the art and mystery of shoe making,'a line of life which, from its peculiar monotony, seems by no means unfriendly, as experience has shewn, to the progress of intellectual acquirement. The strength of mind for which young Cranch had been distinguished from his childhood was now constantly struggling with the adverse circumstances of his situation, but every moment which could be stolen from his daily labour, was devoted to the few books which he had found means to collect; the study of natural history was that in which he mostly delighted; and, even at this early period of his life, he was able to draw up correct descriptions of all the insects he could procure in the neighbourhood of Kingsbridge. Without other assistance than books, he had acquired sufficient knowledge of Latin and French, to enable him to understand thoroughly those lan guages, when made use of by zoological writers, and to employ them himself, in describing objects of natural history. He had acquired also a general knowledge of astronomy. But, while thus eagerly endeavouring to grasp at science, every thing tended to depress, and nothing to encourage him. However, he had the fortitude to persevere; and continued, in spite of every obstacle, silently and sedulously, unnoticed and unknown, to nourish his ruling passion, the love of knowledge.

At the expiration of his apprenticeship, he went up to

London, with the professed view of improvement in the art of shoemaking, but in reality with higher objects and better hopes, though he hardly ventured to own them to himself. The manners and morals of his fellow workmen were ill suited to his feelings and pursuits, and served only to increase his dislike for the employment to which he had been doomed. But it was some consolation to reflect that he was in the great mart of human knowledge, and though unfriended, and a stranger, he found that information flowed in upon him on every side. His mind was filled, but not satisfied; every museum, auction room, and book stall, every object to which his attention was called he visited with a rapid and unsatiable curiosity, gleaning information wherever it was to be had, and treasuring it up with systematic care. His account of what he observed in the capital is said to exhibit an obvious and striking proof of an inquisitive, diligent, and discerning mind. A person of this stamp could not long remain in London without meeting with kindred spirits. One of these associates, speaking of Cranch, observes, "our conversations and philosophic rambles near London, have often called forth such observations and disquisitions from him on the various qualities, attributes, combinations, provisions and arrangements of nature, as marked vast comprehension, as well as the most delicate subtilties of discrimination in an intellect, which seemed indeed to be calculated to grasp magnitude and minutiæ with equal address, and which could at once surprise, delight, and instruct."

After a residence of some time in London, he returned to the haunts of his childhood; but it was soon discovered how little chance the "boot maker from London" had of eclipsing even his humble rivals who had never lost sight of the smoke of their native hamlet; but he had no alternative, he must eat to live, and work at his trade to be able to eat; his labour however produced him little more than a bare subsistence, and every moment that he could venture to take from it, was dedicated to his favourite pursuit.

Shortly, however, his domestic circumstances were favourably improved by marriage. His workshop was now consigned wholly to his journey men, while he was sedulously and successfully collecting objects of natural history. No difficulties or dangers impeded his researches ; he climbed the most rugged precipices; he was frequently lowered down by the peasants from the summits of the tallest cliffs; he waded through rapid streams; he explored the beds of the muddiest rivers; he sought the deepest recesses. He frequently wandered for whole weeks from home, and often ventured out to sea for several days together, entirely alone, in the smallest skiffs of the fishermen. No inclemency of weather; no vicissitudes of "storms and sunshine," ever prevented his fatiguing pursuits; the discovery of a new insect amply repaid the most painful exertions. Several papers in the "Weekly Entertainer," a little work which accompanies one of the most popular of the western newspapers, were written by him; and by these, and his collection of subjects in natural history, he gradually became better known, and his talents duly appreciated by the most able naturalists. Of this the following extract of a letter to the editor, from Dr. Leach, of the British Museum, bears ample and honourable testimony.

seum.

"In 1814, Mr. Montagu and myself, together with Mr. C. Prideaux, visited Mr. Cranch, for the purpose of seeing his MuWe were all astonished at the magnitude of his collection of shells, crustacea, insects, birds, &c. collected entirely by himself, and still more so with the accuracy of their classifi cation and with the remarks made by this self-educated and zealous individual. He conversed on all subjects connected with natural history, with modesty, but at the same time, with that confidence which is the result of knowledge. Quite delighted with having made his acquaintance, I left him with a resolution to cultivate a correspondence with him on the subject of our favourite pursuit. On the following morning, I received a note from him, offering me any specimens that might be wanting and that he could supply, to my collection.

"Soon after this meeting, I was appointed to the British

Museum, when Mr. Cranch applied to me to endeavour to obtain for him some situation in that institution, which would enable him to cultivate the study of natural history on a more extended scale; but as no vacancy existed, and as I found his demands for employment come within the limits of my pocket, I proposed that he should undertake to investigate the coasts of Devon and Cornwall for marine productions; and eventually to make a tour of Great Britain, with the same view; at the same time I promised to recommend him to the first situation that might occur, to enable him to obtain the object of his ambition.

He

"On receiving my letter he immediately discharged his jour neymen, and converted his manufactory of boots and shoes into apartments for the reception and preservation of such objects of natural history as his daily exertions might procure. kept up a continual communication with the fishermen of Plymouth, and constantly received from them baskets filled with the rubbish they dregged from the bottom of the sea; and this he examined with diligence and attention, preserving all the new objects that he discovered, and making descriptions of them. He visited occasionally, the Brixham, Plymouth, and Falmouth fishermen, and made excursions with them. He very often left Kingsbridge in an open boat, and remained absent for a long time together, during which, he dregged when the tide was full, and examined the shores when it was out. At night he slept in his boat, which he drew on shore; and when the weather was too stormy for marine excursions, he would leave his boat and procred to examine the country and woods for insects, birds, &c. The remarks with which he accompanied the infinity of new objects which he discovered, are invaluable; many of them have been and the rest shall be hereafter made public."

In this way was Mr. Cranch employed for the collection of natural history in the British Museum, at the time when the expedition to the Congo was planned: for such an expedition, a person of this description was invaluable, and Dr. Leach recommended him to Sir Joseph Banks, as one in every way fitted for the undertaking. On his part, an appointment so suited to his pursuits and so flattering to his hopes, was the height of his