The repulsion of the machine was compared to the repulsion in a partial vacuum, in hydrogen, in carbonic acid, and in rarefied carbonic acid. The former experiments the same day were on the rise of a thermometer heated by a coil of platinum wire in different gases. On September 21 the Note-Book says: _An Experiment to Decompose Muriatic Acid Gas._--A balloon having three openings, to one of which a stopcock was cemented, and in the other two were corks containing wires, so adapted to each other that a contact might be made. Pieces of well-burnt charcoal were fastened to the ends of the wires. The apparatus, being air-tight, was exhausted and filled with hydrogen; another exhaustion being made, the balloon was filled with oxymuriatic gas from a gas-holder, with which it was connected by means of a stopcock. The two wires being joined to the voltaic apparatus and a contact of the charcoal made, the ignition was brilliant without any apparent combustion; white fumes were presently produced, which in a short time disappeared again, and were afterwards, during the remaining time the experiment was in hand, only formed when two new points of charcoal came in contact, or when the flame played on the copper wire which fastened the charcoal. The light emitted was a brilliant yellowish colour, frequently assuming a fine lake. After an hour’s time the gas appeared unaltered, of its original colour. The higher parts of the pieces of charcoal were covered with a fine greenish-yellow powder, otherwise unaltered. Tin-leaf thrown in through one of the openings began immediately to form with the oxymuriatic acid gas the fuming liquor of Libavius. When shook it inflamed. On September 23, 1809, in a letter to Mr. Children, he mentions this experiment, and says ‘it is as difficult to decompose as nitrogen, except when all its elements can be made to enter into new combinations.’ On October 3, among ‘the hints for experiments’ in the Note-Book is this, to detonate together hydrogen and oxymuriatic acid. Another Bakerian lecture was given, and then he continued his researches on ammonia. On November 24 ‘experiments to be in progress’ are thus entered in the Laboratory Book: 1. To decompose sulphuretted hydrogen by electricity in an apparatus by which the results can be accurately known. 2. To pass potassium through ignited powdered quartz. 3. To decompose muriatic acid gas by potassium, so as to ascertain the quantity of hydrogen formed. 4. To weigh ammonia, hydrogen, and nitrogen, sulphuretted hydrogen and gaseous fluoric acid, nitrous oxide, and oxymuriatic acid gas. 5. To make a series of experiments upon the ores and products of cast iron. 6. To ascertain with greater precision than has been yet obtained the nature of the acid matter formed in pure water, oxygenated or not.