The chemical laboratory of the Royal Institution, as the scene of Davy’s greatest discoveries--discoveries which mark epochs in the development of natural knowledge--will for ever be hallowed ground to the philosopher. The votaries of Hermes have raised far more stately temples: to-day they follow their pursuit in edifices which in architectural elegance and in equipment are palaces compared with the subterranean structure which lies behind the Corinthian façade in Albemarle Street. But to the chemist this spot is what the Ka’ba at Mecca is to the follower of Mohammed, or what Iona was to Dr. Johnson: and, if we may venture to adapt the language of the English moralist, that student has little to be envied whose enthusiasm would not grow warmer or whose devotion would not gain force within the place made sacred by the genius and labours of Davy and Faraday. And yet, were these great men to revisit the scene of their triumphs, they would hardly recognise it, so completely altered is it by adaptations and rearrangements rendered necessary by their discoveries. How it appeared in their own time may be seen from the illustration on page 91, taken from a water-colour drawing by Miss Harriet Moore, in the possession of the Managers of the Royal Institution. [Illustration: CHEMICAL LABORATORY OF THE ROYAL INSTITUTION IN DAVY’S TIME.] The first year of the century is memorable for the invention of the voltaic pile, and for the discovery, by Nicholson and Carlisle, on April 30th, 1800, of the electrolytic decomposition of water. As Davy said, “the voltaic battery was an alarm-bell to experimenters in every part of Europe; and it served no less for demonstrating new properties in electricity, and for establishing the laws of this science, than as an instrument of discovery in other branches of knowledge; exhibiting relations between subjects before apparently without connection, and serving as a bond of unity between chemical and physical philosophy.” The capital discovery of Volta was made known in England at the earliest possible moment through the mediation of Sir Joseph Banks, and the study of voltaic electricity, its effects and applications, was immediately afterwards entered upon by many Englishmen of science with great zeal and ardour. Davy at this time had just completed his work on Nitrous Oxide; and, powerfully impressed with the significance of Nicholson and Carlisle’s observation, he at once turned his attention to the subject, and even before leaving Bristol he had sent a number of short papers on what was then usually termed the galvanic electricity to Nicholson’s Journal. He showed that oxygen and hydrogen were evolved from separate portions of water, though vegetable and even animal substances intervened; and conceiving that all decomposition might be polar, he “electrised” different compounds at the different extremities, and found that sulphur and metallic substances appeared