TRANSACTIONS OP THE SECTIONS. 4f 



as would be indicated by an analysis of their ashes, but it was frequently much greater 

 as to quantity, than could be accounted for by any idea of merely supplying what was 

 to become an actual constituent of the crop. 



If then we would attain by the aid of science a rational system of agriculture, the 

 actual facts of the art itself, — the indications of direct experiments in the field, — and 

 the study of the functional actions of plants and animals, must each receive a due share 

 of our attention. In fact, chemistry alone would do little for practical agriculture. 



On Liquid Diffusion. By Professor Thomas Graham, M.A., F.R.S., 



Professor Graham gave a view of some of the unpublished results, to ascertain 

 whether solutions of saline bodies had a power of diffusion among liquids, especially 

 water. The apparatus may be stated to be a bottle with ground edges, to be filled 

 with a weak solution of the saline matter (and closed by a plate of glass), and placed 

 at the bottom of a glass vessel of water, care being taken to keep the temperature 

 constant. Then, taking a salt of double base, such as the tartrate of potassa and soda, 

 if it had the power of diffusing itself in the water around, he was enabled, by con- 

 verting these bases into chlorides, to ascertain if their diffusion was luiequal, or a 

 decomposition might be effected, as the manner of solution of some substances is known 

 to caiise this kind of unequal decomposition. Taking common salt as a diffiisate, and 

 ascertaining the quantity of chlor-silver to be obtained after a given time, he added 

 one percent, of the acids sulphuric, muriatic, nitric, oxalic, and thus ascertained how 

 far these facilitated the diffusion of the substance or the decomposition of it ; thus 

 chloride of sodium alone yielded 7"65 of muriatic acid ; but add one per cent, of nitric 

 acid, and J 0-99 could be obtained under the same conditions, and proving tlie decom- 

 position of the salt. To forward the analysis of bodies in complicated mixtures, and 

 to elucidate physiological views, he had experimented with the weaker acids, tartaric 

 and oxalic acids, and as muriatic acid was found free in the human stomacli, he had 

 tried lactic acid; but evaporated by heat lactic acid does not decompose common salt; by 

 the aid of this new form lactic acid is seen to possess the power in aqueous solutions. 



Prof. Graham states, the obvious objections to the plan of usefully employing the 

 diffusive power of bodies arose from the time required, and the difficulty in ordinary 

 methods of avoiding alterations of heat ; as temperature increased, it shortened the 

 number of hours, and he employed the water-bath at steady temperatures and periods of 

 seventy-two hours to determine the results. Common salt, having a certain diffusion 

 at 50°, had this doubled at 110°, increasing equally for each 50° to 160° and 240°, 

 when a quantity of four times the muriatic acid was obtained to that, at the tempera- 

 ture of 50°. 



On some Theoretical and Practical Methods of determining the Calorific Effi- 

 ciencies of Coals. By Prof. W. R. Johnson, of Washington, U.S. 



Several series of experiments have been made for the purpose of ascertaining the 

 relative values of coals : — 



First, the series performed by the writer of these remarks in the year 1843, and 

 published in 1844 at Washington ; second, that of Sir H. T. Ue la Beche and Dr. Lyon 

 Playfair of London, prosecuted in 1845, 1846 and 1847, and published in 1848 ; third, 

 that of the same experiment published in 1849 ; and fourth, the series detailed in their 

 final report of the present year. The first of the series embraces direct trials of eva- 

 porative power of forty varieties of coal, the second of twenty-seven, the third of thirty- 

 eight, and the fourth of forty-three ; hence we have the means of comparing the prac- 

 tical evaporative power with the results of analysis in the case of one hundred and 

 forty-seven different samples of coal, varying in their composition from the hardest 

 anthracites, through the softer varieties of the same, and through semi-bituminous 

 coals, to those of the most highly bituminous class. We have also in the series coals 

 varying much in the amount of their earthy or incombustible ingredients, as well as in 

 that of their sulphm-, water and ammoniacal compounds. 



It may be proper to examine whether we have yet attained to anytlaw of relation 

 between the actual and the computed heating powers, or whether it be still necessary 

 to have recovn-se to the steam-boiler itself to determine the efficiency of any new 

 variety of coals. The Commissioners at London have expressed the opinion that the 

 element %<?ro(/ew exercises in the case of the Newcastle coals " a very essential imports 



