'In all chemical investigations, it has justly been considered an important object to ascertain the relative weights of the simples which constitute a compound. But unfortunately the inquiry has terminated here; whereas, from the relative weights in the mass, the relative weights of the ultimate particles or atoms of the bodies might have been inferred, from which their number and weight in various other compounds would appear, in order to assist and to guide future investigations, and to correct their results. Now it is one great object of this work to show the importance and advantage of ascertaining the relative weights of the ultimate particles, both of simple and compound bodies, the number of simple elementary particles which constitute one compound particle, and the number of less compound particles which enter into the formation of one more compound particle. If there are two bodies, A and B, which are disposed to combine, the following is the order in which the combinations may take place, beginning with the most simple, viz.: 'The following general rules may be adopted as guides in all our investigations respecting chemical synthesis . . .' Page 214. . . . 'From the application of those rules to the chemical facts already well ascertained, we deduce the following conclusions: Ist. That water is a binary compound of hydrogen and oxygen, and the relative weights of the two elementary atoms are I: 7, nearly; 2nd. That ammonia is a binary compound of hydrogen and azote, and the relative weights of the two atoms are as I : 5, nearly; 3rd. That nitrous gas is a binary compound of azote and oxygen, the atoms of which weigh 5 and 7 respectively; that nitric acid is a binary or ternary compound according as it is derived, and consists of one atom of azote and two of oxygen, together weighing 19; that nitrous oxide is a compound similar to nitric acid, and consists of one atom of oxygen and two of azote, weighing 17; that nitrous acid is a binary compound of nitric acid and nitrous gas, weighing 31; that oxynitric acid is a binary compound of nitric acid and oxygen, weighing 26; 4th. That carbonic oxide is a binary compound consisting of one atom of charcoal and one of oxygen, together weighing nearly 12; that carbonic acid is a ternary compound (but sometimes binary) consisting of one atom of charcoal and two of oxygen, weighing 19; &c., &c. In all these cases the weights are expressed in atoms of hydrogen, each of which is denoted by unity...? Dalton's New System of Chemistry. Chapter iii. page 216. . . . From the novelty as well as importance of the ideas suggested in this chapter, it is deemed expedient to give plates, exhibiting the mode of combination in some of the more simple cases. A specimen of these accompanies this first part. The elements or atoms of such bodies as are conceived at present to be simple, are denoted by a small circle, with some distinctive mark; and the combinations consist in the juxtaposition of two or more of these; when three or more particles of elastic fluids are combined together in one, it is to be supposed that the particles of the same kind repel each other, and therefore take their stations accordingly.' CHAPTER X. Intermediate Epoch. THE early times up to Dalton have been perhaps sufficiently dwelt on, and it would less break the progress of discovery as begun by Dalton if we took a rapid leap to the time of Joule's earlier life. There was however an intermediate period, which we cannot at present examine fully. It has been impossible to give it that attention which it certainly deserves as being interesting to Manchester especially; but considering the time required, the later histories of Manchester which have appeared, and the fact also, which must be confessed, that the results did not promise to be so interesting to the present writer as those on which he has dwelt, although perhaps more so to others, feeling too that it touches too much on the memories of the living, it has been decided to pass over even more characters than we have hitherto neglected. Part of this intermediate time might be called the engineering period, and we shall begin with a notice relating to an eminent engineer of the earlier years, who probably did much to bring others after him. James Watt, Junior. For 1790 we find Mr. James Watt secretary of the Society along with Dr. Ferriar. This was the son of him who made the steam-engine a power in the world; he seems for a time to have represented his father in Manchester. There were at one time a few sheets written by him amongst the Society's papers, but they do not at present appear; and unfortunately the Society has none of that correspondence which it was once proud of. This is strange. The reason of the presence of Mr. Watt, junr., in this town seems to be shown by the allusion in the following letter but he does not seem to have stayed long, and we know that he succeeded to his father's business, and lived a long and successful life. He was generally called Watt of Aston Hall. It is of interest to read this letter, and Mr. Muirhead's remarks, as it shows distinctly that Watt had found the only true method of 'burning smoke,' namely, giving it heat and air at the same time. If this is attended to, smoke will be burnt; those who do not see this and depend on form and shape of brick or iron, are deceived. Those who give heat and air always succeed. From The Life of James Watt, by James Patrick 'It is astonishing,' writes his son Mr. James Watt to him from Manchester in 1790, 'what an impression the smoke-consuming power of the engine has made upon the minds of everybody hereabouts; nobody would believe it until the engine was set a-going, and even then they scarcely trusted to the evidence of their senses. would be diverted to hear the strange hypotheses which have been started to account for it. However, it has You answered one extremely good end: it has made your engines general topics of conversation, and consequently universally known, which they were by no means before in this country.' On June 14, 1785, Watt took out a patent 'for certain newly improved methods of constructing furnaces or fire-places for heating, boiling, or evaporating of water and other liquids which are applicable to steamengines and other purposes, and also for heating, melting, and smelting of metals and their ores, whereby greater effects are produced from the fuel, and the smoke is in a great measure prevented or consumed,' which newly improved methods he describes to consist in causing the smoke or flame of the fresh fuel, in its way to the flues or chimney, to pass, together with a current of fresh air, through, over, or among fuel which has already ceased to smoke, or which is converted into coke, charcoal, or cinders, and which is intensely hot, by which means the smoke and grosser parts of the flame, by coming into close contact with, or by being brought near unto the said intensely hot fuel, and by being mixed with the current of fresh or unburnt air, are consumed or converted into heat, or into pure flame free from smoke.' 'I put this in practice,' he continues, 'first, by stopping up every avenue or passage to the chimney or flues, except such as are left in the interstices of the fuel, by placing the fresh fuel above, or nearer to the external air, than that which is already converted into coke or charcoal; and by constructing the fire-places in such manner that the flame, and the air which animates the fire, must pass downwards, or laterally, or horizontally, through the burning fuel, and pass from the lower part, or internal end or side of the fire-place, to the flues or chimney. In some cases, after |