material we start with, and I think I have taken a step in the right direction in bringing before you, for the first time, this new form of still. Before describing the apparatus in detail, I think a few words of explanation as to the advantages to be gained by this form of still over those at present in use will not be out of place. In distilling mineral oils as at present, the contents of your still are gradually getting the denser as you proceed, and by the time you are three-fourths through with the distillation you have a very viscid material to deal with, and this, from its non-conducting properties and density, has a great tendency to cling to the bottom of the still and prevent the necessary heat passing to evaporate it quick enough, and hence you require to force more heat into the still to overcome the resisting action of the thick residue. In this way the sides of the still, above the level of the oil inside, get excessively heated, and the oil vapours coming in contact with this radiant heat are very apt to get broken down to a considerable extent, and thus yield a degraded distillate. If you pump in fresh oil on the top of this heavy residue, I find this oil does not, to any great extent, dissolve the residue in the still, but lies on the top of it; and while this latter portion is being distilled, a granular pitch is being formed at the bottom of the still, and if you push your heat further you will convert this gradually into coke of a very hard nature, and you will have a considerable loss through the formation of permanent gas. I have seen this very beautifully illustrated on taking off the end of a horizontal still I was working with. The layer of coke next the skin of the still was exceedingly dense in character, and it gradually got less dense as it increased in thickness, and towards the upper surface it was quite granular, and this again was topped with a pitch which remained plastic on cooling. You will thus see that practically all the heat which was distilling the oil on the surface was obtained from the upper sides of the still, and not from the bottom-very bad economy of heat indeed. This excessive heat at the end of the distillation is the main cause of the short life of many of our oil stills. With regard to this new form of still which I have the honour to place before you (see Plate No. 4), I think I have surmounted these difficulties. You will observe that in vertical section it takes the form of a cross, +, the head of which forms the attachment of the Swan neck; the wings forming the distilling chamber, and the tail-piece being that portion by which the pitchy residues are kept separate from the lighter oil under distillation. By means of a ball-cock arrangement, the still is kept always at a uniform depth. The heat is applied to the under surface of the wings all round the still, and as this distillation goes on, the heavy residue, which forms, gradually finds its way to the bottom of the tail-piece, and remains there away from the source of heat, and when sufficiently heavy can readily be removed by the cock arrangement found there for that purpose. In this way you should never be troubled with coke forming, and your still should always remain clean. The depth of oil, through which the distilling heat has to pass, is always a constant factor, and the nature of the oil under the action of this heat is pretty nearly uniform. The bottom of the main body of the still or distilling chamber, as I call it, is inclined downwards and inwards, and this facilitates the withdrawal of the residual matter from this chamber, as it is formed, to the cooler region at the tail-end of the still. You thus avoid all forcing of fires; no part of your still gets unduly heated; your gases have a shorter travel; and you work practically with a uniformly steady heat, the energy of which is employed in doing useful work. I am strongly convinced, from the experiments I have already made, that such a form of still as I have placed before you this evening, whether worked in conjunction with a vacuum pump or not, would produce from a given oil a larger percentage of heavier oils, of greater viscosity, and also of high melting-point paraffin, than any other still at present in use. REFERENCES TO PLATES. PLATE NO. 1.-Figures 1 and 2 are respectively a transverse vertical section and a longitudinal vertical section of the apparatus. The same reference letters mark the same parts when repeated, two or more similar parts are distinguished by numerals combined with letters. A, boiler still; B1 to B4, compartments in still open at bottom; C, vertical |