V, when required. As seen in Fig. 251 the entire apparatus rests upon four supports b and can readily be placed anywhere. For the purpose of cleaning, the actual burner B can be easily removed and inspected.

The following advantages are claimed for this burner: The attainment and maintenance of a very high temperature; a pure flame without soot and without injurious gases; ready regulation of the intensity of the flame, and a clean and cheap process of working. The apparatus is much used in Baku and on the Volga. Three sizes, of 5.9, 7.87 and 9.84 inches external diameter, are now manufactured. The price of a 7.87 burner in Baku is about $63.00. It consumes about 33 lbs. of petroleum per hour.

Petroleum stoves and furnaces for domestic purposes.

For domestic purposes a great variety of stoves, some of them quite pretentious in size and ornamental in appearance, are already extensively employed. In these, generally, a hightest oil is used. They are mostly employed by small families, and in the summer season, when the heat of a large coal-burning cooking stove would be almost insupportable. The advantages consist chiefly in the fact that as soon as the necessity for the stove ceases, the fire is extinguished without loss of fuel, and as soon as the necessity reappears, the fire is made and in full blast without loss of time. These are two very important desiderata. Besides, there is a positive economy in fuel, to say nothing of superior convenience and cleanliness. In these stoves either round or flat wicks are used, the size of which is proportional to the amount of heat required. The heat generated is quite sufficient for the ordinary purposes of a small family.

Uses of lubricating oils.

The advantges, both pecuniary and beneficial, accruing to modern civilization, from the introduction of the heavy products of petroleum for the lubrication of machinery are hardly

second to those resulting from the introduction of the cheap and beautiful light furnished by its illuminating portion. It would be difficult to exaggerate its importance and value to the textile manufacturer, to the iron industry, and to the railroad interests. The hydro-carbon oils, for the purpose of lubrication, were at first received with but little favor; indeed, the opposition was all but universal. The disagreeable odor always associated with the imperfectly prepared oils first offered, disinclined superintendents of mills and factories to give them a trial, even at prices much lower than those which they were accustomed to pay. Insurance companies, on account of the ex plosible inflammable vapors, said to be inseparably connected with them, refused to take risks, except at greatly increased rates, upon factories where they were employed. The objections urged against their introduction were not wholly without foundation, and incited the manufacturers to increased diligence in removing them. Improved methods of treating these oils soon resulted in greatly improved products; the prolific yield of the crude material from the wells further reduced their market price. Accurate methods of testing their real economic value were discovered and introduced into use, and thus through their real merit in the face of often ignorant opposition, these oils have made their way into general use and favor. It is not to be inferred from what has been said, that animal and vegetable lubricating oils are driven from the market, or are likely to be. They have distinctly important uses, and whether alone or combined with hydrocarbon oils, will still be employed for the purpose of lubrication. Nothing has contributed more rapidly and more effectually to disarm the ignorant opposition before alluded to, than the accurate tests of their working value to which all kinds of machinery oils are now subjected. These have resulted not only in discovering desirable qualities in the hydrocarbon oils hitherto unsuspected, but have pointed out methods by which objectionable features have been either wholly removed or greatly modified.

Prof. R. H. Thurston, in his "Treatise on Friction and Lost

Work in Machinery and Mill Work," furnishes the following characteristics of a good lubricating material:

1. Enough "body" or combined capillarity and viscosity to keep the surfaces between which it is interposed from coming in contact under maximum pressure.

2. The greatest fluidity consistent with the preceding requirements, i. e., the least fluid-friction allowable.

3. The lowest possible coefficient of friction under the conditions of actual use, i. e., the sum of the two components, solid and fluid-friction, should be a minimum.

4. A maximum capacity for receiving, transmitting, storing, and carrying away heat.

5. Freedom from tendency to decompose or to change in composition by gumming or otherwise on exposure to the air or while in use.

6. Entire absence of acid or other properties liable to produce injury of materials or metals with which they may be brought in contact.

7. A high temperature of vaporization and of decomposition, and a low temperature of solidification.

8. Special adaptation to the conditions, as to speed and pressure, of rubbing surfaces, under which the unguent is to be

used.

9. It must be free from grit and from all foreign matter.

The consumer will readily recognize in the above all the desirable qualities that he requires, and the manufacturer those points of excellence he aims to secure in his products. As to what lubricant to use under certain specified conditions of temperature, speed, and pressure, a practical trial under these conditions will be the best teacher.

The managers of numerous railroads hold, even at the present time, to the principle which, however, has not been practically proven, that for lubricating passenger, mail and baggage cars, vegetable oil or a mixture of vegetable and mineral oils should be used. Among some the opinion prevails that for lubricating cars running at greater velocity, a better quality of oil has to

be used, it being supposed that with an increase in the velocity there is greater danger of hot-running. Opinions differ also in regard to the choice of lubricants for locomotives; the position of the management of many railroads being such that experimenting never ceases. Exact experiments on a large scale with entire trains have not been made, so that theoretical speculations are frequently the only guide. Joseph Grossman, in his work "Die Schmiermittel," arrives at some novel conclusions. His deductions, based upon Coulomb's experiments and the more recent examinations of R. H. Thurston, show that from a theoretical standpoint it would seem rational to lubricate freight cars with a better, though more expensive quality of oil, and passenger cars with the ordinary cheap oil. This, however, cannot be carried out in every case, since with the greater number of freight cars used it would be scarcely possible to lubricate them with expensive oil and the smaller number of passenger cars with cheap oil. For railroads with a level track or slight grades, the use of a better quality of oil may therefore be recommended, while railroads with steeper grades, which can derive no advantage from the use of expensive oils, may secure an economical advantage by the choice of as cheap an oil as possible; in the first case a very thinly-fluid, but as viscous an oil as possible, should be selected, and in the latter very thicklyfluid oils.

For locomotives it is advisable for economical reasons to use two kinds of oil. For cylinders and slide valves, oils distinguished by a very high flashing point should only be used, vegetable and animal oils being best for the purpose, since they do not evolve inflammable vapors at the high temperature (356° F.) which prevails in the cylinder. On the other hand, mineral oils have stood the test only in very rare cases, tolerably favorable results having been attained only with special fractions, or still better with thoroughly refined residuum. This furnishes one of the best illustrations of the principal difference between vegetable and mineral oils. With the use of the former the slide valves and locomotive always feel greasy,

while, after the same working time, mineral oil leaves the sides of the cylinders dry, they frequently appearing corrugated, and coke-like separations are observed on the slide-valves and pistons. This is largely due to the fact that at these high temperatures, mineral oils, as compared with vegetable oils, lose so much of their viscosity that they adhere in a scarcely perceptible manner to the sides and suffer partial decomposition in consequence of the prevailing high temperatures and the pressure to which they are exposed, this phenomenon being also frequently observed in large stationary engines. Hence the annoying buzzing of the cylinder can be traced either to an insufficient consumption of lubricating oil or to readily decomposable oils, the natural consequence being a considerably larger consumption with the use of mineral oils. For the cold parts of locomotives pale mineral oils and thoroughly refined residuum are very suitable, experience having shown that the best mineral oils for the purpose are such which at 122° F. show the same viscosity as rape oil at the ordinary temperature.

For lubricating marine engines, mineral oils are suitable only in very rare cases. The high temperatures prevailing in the engine-rooms require lubrication, especially of high-pressure cylinders, with very viscous mineral oil of especially good quality and high flashing point, or still better, with animal oil or a mixture of both.

For the lubrication of the cold parts of stationary engines, the well-known mineral machine oils are very suitable and, with the exception of the slide-valves and cylinders, may be used on every part of the engine, all principal transmissions and shafts, while the cylinder and piston should be lubricated with vegetable oils, or still better with pure mineral fats free from acid, the so-called crude vaselines. As previously mentioned, pale oils are to be preferred to dark oils, if for no other reason than that dangerous friction of parts of the engine is indicated by the change in the color of the oil caused by small metallic splinters.