This battery, when the cells were filled with sixty parts of water mixed with one part of nitric acid, afforded a series of brilliant and impressive effects. When pieces of charcoal, about an inch long, and one-sixth of an inch in diameter, were brought near each other, (within the thirtieth or fortieth parts of an inch,) a bright spark was produced, and more than half the volume of the charcoal became ignited to whiteness, and by withdrawing the points from each other a constant discharge took place through the heated air, in a space equal at least to four inches, producing a most brilliant ascending arch of light, broad and conical in form in the middle. When any substance was introduced into this arch, it instantly became ignited; platina melted as readily in it as wax in the flame of a common candle; quartz, the sapphire, magnesia, lime, all entered into fusion; fragments of diamond, and points of charcoal and plumbago rapidly disappeared, and seemed to evaporate in it, even when the connexion was made in a receiver exhausted by the air-pump; but there was no evidence of their having previously undergone fusion. All the phenomena of chemical decomposition were produced with intense rapidity by this combination. When the points of charcoal were brought near each other in non-conducting fluids, such as oils, ether, and oxymuriatic compounds, brilliant sparks occurred, and elastic matter was rapidly generated. Among the numerous experiments performed by the aid of this battery, he instituted several, in the hope of decomposing nitrogen; and which are recorded in his Bakerian Lecture of 1809. He ignited potassium, by intense Voltaic electricity, in this gas; and the result was, that hydrogen appeared, and some nitrogen was found deficient. This, on first view, led him to the suspicion that he had attained his object; but, in subsequent experiments, in proportion as the potassium was more free from a coating of potash, which necessarily introduced water, so in proportion was less hydrogen evolved, and less nitrogen found deficient. The general tenor of these enquiries, therefore, did not strengthen the opinion he had formed with respect to the compound nature of nitrogen. It appears from the following letter, that Davy visited his friend Mr. Andrew Knight at Downton, in September 1809. It is introduced in these memoirs principally for the purpose of showing with what boldness he was accustomed to depart from generally received opinions, and to project new theories for the explanation of the most abstruse subjects. TO JOHN GEORGE CHILDREN, ESQ. September 23, 1809. MY DEAR FRIEND, I am about to visit Downton, and shall return by the first of October. I have neither seen nor heard from Lord Darnley, and I conjecture he has not yet returned from Scotland. I wish you great sport in pheasant-shooting, but I trust you have had still nobler game in your Laboratory.