philosophy, whose labors wrought a complete revolution in the science of chemistry. Differing in every respect, they had the same object in view; but their success was as varied as their circumstances.

Of Scheele, the least known of the three, we first proceed to give a short sketch. He was born at Stralsund, in Swedish Pomerania, the ninth day of December, 1742. His parents, though poor, afforded him the advantages of a college education, which he does not seem to have turned to much account. It is probable that his extraordinary modesty prevented him from making that show which is too often considered as the test of real ability. His family considered him well situated with an apothecary of Gottenburg, with whom he entered at the age of thirteen, and remained six years as an apprentice and two as a pupil. A chemical work, which accident. brought in his way, determined the direction of his studies; and in obscurity, he completed some of his greatest discoveries. He was not without his misfortunes and disappointments. On one occasion, a fellow apprentice, in a fit of spite, mingled a detonating powder with some of his materials, and on stealing to his work when all the family were asleep, he accidentally produced an explosion which alarmed the household and discovered his labors. The consequence was, an increase of severity on the part of his master, which operated greatly to retard his progress.

At the age of twenty-seven, Scheele went to Stockholm, already in possession of some of the most important discoveries of the day. The communication of these to the Academy was not received with the attention he expected and really deserved. Disgusted with this attempt, he relinquished all connection with the Academy, and finally removed to Upsal, where Bergman had already acquired a reputation, the fame of which had spread throughout Europe. The accident which introduced these philosophers to each other is worthy of being related.

"Scheele was employed by an apothecary who furnished Bergman with chemical products. The latter, one day, having occasion to use saltpetre, procured it of the apothecary. In using this substance in an experiment, an abundant evolution of red fumes took place, formed, as we now know, by hypo-nitrous acid, but which Bergman did not expect from the nature of the experiment. He was astonished, and imagined that the salt contained some impurity.

He sent it back by one of his pupils, who did not neglect so fine an opportunity of insulting the poor apothecary boy who gave it to him. But Scheele, having heard what had happened, asked for the details of the experiment, and immediately gave an explanation. No sooner was this reported to Bergman than he ran to Scheele, questioned him, and found, to his great surprise and great delight, under the humble apron of an apothecary's clerk, a profound and accomplished chemist a chemist of high rank, to whom were already revealed a number of facts unknown to himself—a chemist who, far from being content with the details of practise, had already developed those notions of the composition of air and the theory of heat which served as the basis of his "Treatise on Air and Fire," in which he has surpassed Priestley and sometimes almost equalled Lavoisier."

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The acquaintance thus formed ripened into the warmest friendship. Bergman sought to advance his young friend. But the sensitiveness and timidity of Scheele withdrew from the contact of the busy world; and not even the offers of the king of Prussia could tempt him from his retreat. A far more suitable opening appeared to him in the small town of Koping, in a pharmacy belonging to a widow. The employment and the quiet of the retreat pleased him. Besides, this person had a little property, and he might aspire to her hand. He removed to Koeping, and established himself with the widow; but found, on examination, that the estate was encumbered with debts, the lady worth nothing, and his promised leisure exchanged for hard work. But, like an honorable man, he never hesitated-made his arrangements, and set to work to pay off the debts. Out of six hundred pounds profit per year, he reserved four hundred for his own wants, and devoted the remainder to chemistry.

Scheele would soon have been forgotten had it not been for Bergman, who no sooner heard of any of his discoveries than he hastened to publish them throughout Europe. Scheele's fame was thus spread far and wide, while he remained almost unknown in his own country.

The peculiar character of the investigations of Scheele was derived from his happy method of interrogating nature, his quick perception, and his skilful manipulation. With the simplest forms of apparatus, for none others were within his reach, he discovered many substances, and so fully demonstrated their properties that little else remained to be determined concerning them. In reviewing the discoveries of

Scheele, we must bear in mind that he was ignorant of the various European languages, except his vernacular and the German. By this and his isolated situation, he was almost entirely cut off from a knowledge of the labors of his contemporaries; and in fact, we find that he re-discovered oxygen a year after Priestley had made it known. The greater merit consequently is to be attached to his chemical skill. It is one thing to follow up the knowledge of the times, and another to carry out the study of a new science unaided; and the latter was in fact the position of Scheele.

The papers of the Swedish chemist are to this day models of investigation; and the important results flowing from them proved their value. For instance, the memoir on the oxide of manganese was the precursor of his discovery of oxygen, chlorine, and barytes. We likewise owe to Scheele the knowledge of the manganesic, arsenic, molybdic, lactic, tartaric, amnic, tungstic, prussic, citric, gallic, and fluosilicic acids. Besides these, he cast new light upon many other substances but imperfectly known before his time. Dumas asserts that not a single error can be detected in his examination of the properties of bodies.

But although infallible in facts, in theory his bias for phlogiston warped his whole philosophy. It would be useless and invidious to dwell upon the few remaining errors of one who accomplished so signal a victory over the ignorance of his time. Moreover, the situation of Scheele was such as to prevent his acquaintance with the new theory; and most probably, had he been a citizen of Paris instead of the humble town of Koeping, his course would have been different. Our author, in endeavoring to elevate his own countryman, is a little too much inclined to undervalue all others.

In the midst of his usefulness-his writings completed the debts of his predecessor paid-death suddenly removed the good and modest Scheele from the scene of his labors. He had married the widow whose fortunes he had so nobly shared, and on the same day was attacked by a severe illness which in four days terminated his life. According to others, he had for some time been aware of his approaching dissolution, and hastened to leave her the legal inheritor of his name and little property. He died the twenty-second of May, 1786, at the age of forty-four.

The second of these contemporaries was Priestley, whose history is too generally known to need repetition in this place.

We never have seen any account of his life, however, in which the true secret of his misfortunes, his errors and his discoveries is so well delineated as in the rapid and brilliant sketch in the work before us.

Priestley was born in 1733. From his infancy, his mind appears to have been warped by strange religious notions; and having with inconceivable rapidity made himself master of the oriental languages, he prepared for the pulpit. His heterodox notions, however, precluded him from associating with any others, and he finally established himself as a sort of independent preacher. After a series of changes and removes, he became acquainted with Franklin by accident while in London, and at the age of thirty-two, commenced the study of electricity. His researches in this branch of science soon obtained him a reputation among learned men, and finally the membership of the Royal Academy.

Soon after this, his residence near a brewery was the means of inducing him to study the properties of fixed air or carbonic acid, immense quantities of which were generated in the brewer's vats. This study led him to perfect the means of manipulation with gases, and to the invention, among other apparatus, of the pneumatic trough, without which our knowledge of this important class of bodies would have remained exceedingly limited.

At this time, Priestley came very near sailing with Captain Cooke upon his second voyage. The great commander was desirous of employing Priestley as chaplain ; but, fortunately for himself and for science, the admiralty found that he was not orthodox. This was the only occasion, says the lively Frenchman, upon which his religious notions rendered him any service.

The career of Priestley as a chemist was rendered singularly brilliant and famous by his discovery of a number of the most important gases. Previously to his time, but two were known, carbonic acid or fixed air, and hydrogen or inflammable air. Possessed of the means of examining the gases evolved under various circumstances, he had but to collect them and determine their properties as fast as his versatile genius could devise new modes of generating them. His discoveries are nitrogen, the binoxide of nitrogen, ammonia and muriatic acid (previously only known in solution), the protoxide of nitrogen, sulphurous acid, oxygen, fluosilicic acid and carbonic oxide. The important part which these gases play in chemical action can give some idea of the value

of his labors. The discovery of oxygen, original with both Priestley and Scheele, may well be considered as the forerunner of the new chemistry.

As to the rest, Priestley was a warm supporter of phlogiston, and adhering to the doctrine with his accustomed tenacity, raised his voice in its favor even after his flight to America.

The most curious feature in the character of this remarkable man, is his constant denial of all knowledge of the science of chemistry, and his assertion that his discoveries were all the result of chance, and the more easily made because he was no chemist. "Nothing is more curious than the perusal of his works. Always disposed to attribute the merit of his discoveries to chance, Priestley affects a great deal of humility, but constantly talks of himself. He pretends to hold his own opinions very cheap, but never abandons one of them, while he attacks with severity those of every one else. his estimation, facts are every thing-he has the greatest regard for them, and always submits to them, provided they are such as he has observed. The facts of others appear to him doubtful and even falsified. He alone is precise, veracious and logical." After this, who will be surprised at his errors in theology or natural science?

The third of these distinguished contemporaries was the immortal Lavoisier,-one of the greatest philosophers the world ever saw. To do justice to the discoveries of the founders of modern chemistry, we should occupy more time than our original purpose would allow. A simple sketch of the nature of his investigations must suffice.

Lavoisier brought all theories to one test-the balance; and while the old chemists had contented themselves with observing the forms of bodies, he first demonstrated that matter, by human power at least, was indestructible, uncreatable; that consequently the mere appearance of substances was not the means of judging what alterations had taken place, but that the evidence afforded by change in weight was unerring. Moreover, he disproved the phlogistic theory, demonstrated the composition of air and water, metallic oxides and acids. The generalization of these facts was the basis of systematic chemistry; and, although not perfect, and in some respects too hasty, has yet furnished a language to the science upon which all farther experience can be grafted, without doing violence to the