In 1778, he pursued his experiments on the property of vegetables growing in the light, to renovate impure air, and on the use of vegetation in this part of the economy of nature. Chemistry is also indebted to him for the method of decomposing metallic oxides by means of hydrogen gas, and for noticing that this gas has the property of dissolving iron. He observed also that lime is less soluble in hot than cold water; and that when a solution of lime in cold water is heated, part of the lime is deposited. In the first volume of his work on air (p. 278), Dr. Priestley has anticipated the idea of Dr. Arnott and Sir J. F. W. Herschel, that electricity, acting on the brain and nerves, may excite muscular action. Dr. Henry, in the memoir already quoted, has remarked, that facts are to be met with in various parts of Dr. Priestley’s works that might have given him a hint of the law, since unfolded by the sagacity of M. Gay-Lussac, “that gaseous substances combine in definite volumes.” From the same memoir we extract the following observations, in conclusion of this short account of Dr. Priestley’s scientific labours:—“He greatly enlarged our knowledge of the important class of metals, and traced out many of their most interesting relations to oxygen and to acids. He unfolded, and illustrated by simple and beautiful experiments, distinct views of combustion; of the respiration of animals, both of the inferior and higher classes; of the changes produced in organized bodies by putrefaction, and of the causes that accelerate or retard that process; of the importance of azote as the characteristic ingredient of animal substances, observable by the action of dilute nitric acid on muscle and tendon; of the functions and economy of living vegetables; and of the relations and subserviency which exist between the animal and vegetable kingdoms.” [Illustration: _Engraved by Rob^t. Hart._ ARIOSTO. _From a Print by Raffaelle Morghen._ Under the Superintendance of the Society for the Diffusion of Useful Knowledge. _London. Published by Charles Knight, Ludgate Street._ ] [Illustration] ARIOSTO. Ludovico Ariosto was born at Reggio, near Modena, in September, 1474. From boyhood he showed a turn for versifying, and a distaste for the severer study of the law, to which he was destined. This repugnance triumphed over the wishes of his father, an Officer in the Duke of Ferrara’s service, and obtained license for him to pursue his own inclinations. His father died about the year 1500, leaving a small inheritance, and ten children, of whom Ludovico was the eldest. Thus, the care of the family, and the education and establishment of its younger branches, devolved upon him; and this onerous and important duty he faithfully performed, while to his mother, who survived his other parent many years, he ever manifested a filial affection.