Attempts accordingly were now made to get over this supposed cause of the losing results, already obtained from the plan of four retorts to one fire-place, by a new series of similar operations, in which the retorts were fixed in such a manner, that those which happened to become injured during the process, might easily and immediately be withdrawn without materially disturbing the rest, and replaced by new ones. The waste of fuel was, it is clear, greatly lessened by the expedient; yet still upon the whole there was no such variation from the general results obtained by the preceding experiments, as to justify the adoption of this plan of increasing the number of retorts worked by one fire-place, on any principle of sound economy. The great obstacle, as the reader will at once perceive, to working more than two retorts, no matter whether cylindrical, or of any of the other forms before named, with economy, by means of one fire-place, evidently arose from the difficulty of conducting the heat by means of flues around the series of retorts, in such a manner that the heat shall act with equal force on all the retorts. It is almost needless to state, that the construction of the fire-places, and the direction of the flues for applying the heat to the retorts, were varied by different workmen, who prided themselves on being able to aid the object in view, but the result always showed even that when the draft of the fire-place was well obtained, the action of the heat upon the series of retorts could not be distributed equally and kept up uniformly, except at a great expence of fuel and vast deterioration of the distillatory vessels. The retorts always became injured more in some parts than in others. The concentration and rapidity of the draught of the fire, beyond a certain velocity was always found highly injurious to the retort, and this observation has been since amply confirmed. In a well constructed furnace, the deterioration of all the retorts in the series is uniform over the whole vessel; no part of the retort is _burnt out_, as the workmen call it, sooner than another part; and whenever the contrary happens, we may pronounce the fire to be badly applied. When there is such misapplication of the heat, the manufacturer cannot depend upon the duration of the distillatory vessel; he is always in a state of uncertainty with regard to their wear and tear, and it not unfrequently has happened, under such circumstances, that a whole series of retorts have become suddenly deteriorated. _Oven plan lately adopted._