Thus, M. Gruner's estimate of the heat evolved is 8 % less than Mr. Bell's, arising from difference of appreciation of the function of the CO2 of the limestone in the blast furnace. As to the sensible heat carried off in the gases, the estimates would be the same, viz., 430 of the lb. units. As to the caloric carried in by the blast, or rather as to the balance of calories for heating the blast, the calculations give 253 calories in the one and 278 in the other, or the temperature of blast would have to be 220° in the one case and 240° in the other.. But the true principles of calorific determinations are so exhaustively displayed in M. Gruner's Studies, that I must refer those who desire to familiarize themselves with these principles and their applications to that source of information, and especially to sections 4 and 16 to 21. Before concluding this note, however, let us examine one case to illustrate the necessity of attending to all the "vital statistics" of furnaces before drawing any conclusions as to their technical economy. Let us take for example Clarence furnace 1866 and Consett This table shows that in a technical point of view there is no practical difference in the economy of working in the two furnaces. The greater yield of the Consett furnace is another question. The rate of driving, calculated by the capacity of furnace per ton of yield, is as 1·75 for Consett against 1 at Clarence. Why one furnace can be driven faster than another is as yet unexplained. At Cleveland the pressure of the blast was 2-75 lbs. as at Consett, but the area of the twyres at Consett was 80 square inches, while at Clarence it was 50. 80 is to 50 as 1.60 to 1, but it would require 80 to 46, to give the ratio of faster driving, viz., 1.75 to 1. This is a subject well worthy the attention of iron-masters and their managers. It will not be without interest to mention here, in reference to the economy of fuel in blast furnaces, that the recorded consumption of coal per ton of forge iron produced has been, at the Dowlais Ironworks, as given on the authority of the late Mr. Truran by Dr. Percy, and as given by Mr. Menelaus, the present manager of these vast works, as follows: Or in three successive generations as 5 2: 1. Again, let us call to mind that 24 66 Osnabrück (Georg-Marienhutte) (C=8040) 25·5 These are a few illustrations to prove that the minimum quantity of fuel required can only be determined approximately for each particular case, of which all the vital statistics are known. Capacity, height, temperature of blast, are all subordinate to design of furnace, quality of material, and skill in management. The history of the hot blast-the different apparatus for applying it-its effects on the progress of iron manufacture— and its theory, I feel reluctantly obliged to reserve for further consideration. 2. Caloric.-Determination of Caloric of Combustion. ...CO burned gives x 2403 =5607. Hence, for the combustion of 1 lb. C to CO we have 8080-5607=2478 calories by calculation. IRON. Cals. 1 lb. iron burned to Fe3 O1 (magnetic oxide) gives 1648, Dulong... Fe203=1854 66 to FeO (protoxide)=1352 Favre and Silbermann, " =2028 7437 =1859 The mean of which experiments and calculation |