essential to success.  At present seventy-two locomotives are running with petroleum firing; ten of them are passenger engines, seventeen are eight-wheel coupled goods engines, and forty-five are six-wheel coupled.  As might be expected, several points have arisen which must be dealt with in order to insure success.  For instance, the distance ring between the plates around the firing door is apt to leak, in consequence of the intense heat driven against it, and the absence of water circulation; it is therefore either protected by having the brick arch built up against it, or, better still, it is taken out altogether when the engines are in for repairs, and a flange joint is substituted, similar to what is now used in the engines of the London and Northwestern Railway.  This arrangement gives better results, and occasions no trouble whatever.

Storage of petroleum.—­The length of line now worked with petroleum is from Tsaritsin to Burnack, 291 miles.  There is a main iron reservoir for petroleum at each of the four engine sheds, namely at Tsaritsin, Archeda, Filonoff, and Borisoglebsk.  Each reservoir is 66 ft. internal diameter and 24 ft. high, and when full holds about 2,050 tons.  The method of charging the reservoir, which stands a good way from the line, and is situated at a convenient distance from all dwelling houses and buildings, is as follows:  On a siding specially prepared for the purpose are placed ten cistern cars full of oil, the capacity of each being about ten tons.  From each of these cars a connection is made by a flexible India rubber pipe to one of ten stand pipes which project 1 ft. above the ground line.  Parallel with the rails is laid a main pipe, with which the ten stand pipes are all connected, thus forming one general suction main.  About the middle of the length of the main, which is laid underground and covered with sawdust or other non-conducting material, is fixed a Blake steam pump.  As soon as all the ten connections are made with the cistern cars, the pump is set to work, and in about one hour the whole of the cars are discharged into the main reservoir, the time depending of course upon the capacity of the pump.  All the pipes used are of malleable iron, lap-welded, and of 5 in. internal diameter, having screwed coupling muffs for making the connections.  At each engine shed, in addition to the main storage reservoir, there is a smaller distributing tank, which is erected at a sufficient height to supply the tenders, and very much resembles the ordinary water tanks.  These distributing tanks are circular, about 81/2 ft. diameter and 6 ft. high, and of 1/4 in. plates; their inside mean area is calculated exactly, and a scale graduated in inches stands in the middle of the tank; a glass with scale is used outside in summer time.  Each inch in height on the scale is converted into cubic feet, and then by means of a table is converted into Russian poods, according to the specific gravity at various temperatures.  As it would be superfluous