SCIENCE. 



155 



oval, not an ellipse; a new illustration, in Dr. Hill's opin- 

 ion, of the fact that the ability of members of two groups of 

 forms to assume an intermediate form affords but a very 

 slight presumption, if any, for a community of origin in the 

 group. 



FRICTION OF LUBRICATING OILS. 



By C. J. H. Woodbury. 



The resistance existing between bodies of fixed matter 

 moving with different velocities or directions presents itself 

 in the form of a passive force, which results in the diminu- 

 tion or destruction of opponent motion. Modern science 

 has demonstrated that this destruction is only apparent, 

 being merely the conversion of the force of the moving 

 body into the oscillation of the resisting obstacle or into that 

 molecular vibration which is recognized as heat. Direct 

 friction refers to the case where the two bodies are in actual 

 contact and mediate friction where a film of lubricant is in- 

 terposed between the surfaces, and it is this which applies 

 to nearly every motion in mechanics where bodies slide 

 upon each other. The coefficient of friction is the relation 

 which the pressure upon moving surfaces bears to resist- 

 ance. Mr. Woodbury limited his discussion to a descrip- 

 tion of the apparatus for measuring the friction of lubrica- 

 ting oils, the method of its use and the results obtained 

 with a number of oils in the market which are used for 

 lubricating spindles. Previous investigation of nine 

 different oil-testing machines used showed that none 

 of them could yield consistent duplicate results in fur- 

 nishing the co-efficient of friction. The paper mentioned 

 the circumstances which must be known or preserved 

 constant, — temperature, velocity, pressure, area of frictional 

 surfaces, thickness of the film of oil between the surfaces, 

 and the mechanical effect of the friction. The radiation of 

 heat generated by friction must be reduced to a minimum, 

 and no oil should be allowed to escape till subjected to 

 attrition. Therefore a dynamometer is required which is 

 instantaneous and automatic in its action. Mr. Woodbury 

 described in detail the construction of his instrument and 

 the mode of its operation, which was too elaborate to be 

 reproduced in an abstract. The operation of the machine 

 under equal conditions with the same oil gives results 

 which are as closely consistent with each other as could be 

 expected from such physical measurements. Much of the 

 slight irregularity was due to the variable speed of the en- 

 gine. The results were remarkably uniform, but they do 

 not agree with the laws of friction, as given in works on 

 mechanics, but the co-efficient of friction varies in an in- 

 verse ratio with the pressure. Friction varies as the area, 

 because the adhesiveness of the lubricant is proportional 

 to the area, and the resistance due to this cause is a larger 

 fraction of the total mechanical effect with light than with 

 heavy pressures. The lubricant used is one of the most 

 important factors in the cost of power. In the present con- 

 dition of engineering science it is impossible to state what 

 exact proportion of the power used by a mill is lost in 

 sliding friction, but in a print-cloth mill only about 25 per 

 cent, of the power is utilized in the actual processes of 

 carding, spinning and weaving (he fibre, not including the 

 machinery engaged in the operation, leaving 75 per cent, of 

 the power as absorbed by the rigidity of the belts, the re- 

 sistance of the air and friction. Mr. Woodbury concludes 

 that the successful operation of a spinning frame is far 

 more closely dependent upon the individual management 

 in respect to the conditions of band-tension, lubrication 

 and temperature of the spinning room than all other causes 

 combined. Not that some forms of spindle are not supe- 

 rior to others, but without wise supervision the most desir- 

 able forms of spindle must fail to show the merits due to 

 the skill of their promoter. The lubricating qualities of an 

 oil are inversely proportional to its viscosity ; the endurance 

 of a lubricant is, in some degree, proportional to its adhe- 

 sion to the surfaces forming the journal. An ideal lubri- 

 cant, in these respects, would be a fluid whose molecules 

 had a minimum cohesion for each other, and a maximum 



adhesion for metallic surfaces. Viscous oils adhere more 

 strongly to metal surfaces, hence it is obligatory to use such 

 thick lubricants on heavy bearings. With light pressures 

 more fluid oils are admissable, and in all cases the oils 

 should be as limpid as possible. Oils with great endurance 

 are likely to give great fractional resistance, and in the en- 

 deavor to save gallons of oil, many a manager has wasted 

 tons of coal. The true solution of the problem of lubrica- 

 ting machinery is to ascertain the consumption of oil and 

 the expenditure of power, both being measured by the same 

 unit, namely, dollars. Mr. Woodbury detailed his experi- 

 ments in measuring the fluidity of oils, and gave the data 

 for determining the safety and efficiency of a lubricant. 



THE LAW OF LAND-FORMING ON OUR 

 GLOBE. 



By Prof. Richard Owen, M.D., LL.D.* 



The truth of a general law can best be proved by such a 

 large collection of co-incident facts as to carry conviction to 

 the scientist. But in a synopsis all that can be done is to 

 state the law and suggest a few prominent demonstrations, 

 leaving it for the reader to trace with compasses or string, 

 on a good globe or large map of each separate continent, 

 those phenomena presented, and such other analogous de- 

 tails as may suggest themselves. 



General Law: The land shows itself above the ocean level, 

 in definite multiple proportions , by measurement ; the unit is 

 the angular difference betiveen the axis of revolution and the 

 axis of progression. 



For convenience, as that angle has been lessening for 



some centuries, we might call it 24°= 3 £ 5 a °. 



The greatest width and length of continents =3X24° = 72° 

 — 2.&0. 

 — s 



Consequently, the radius for continents = 36° = a , £ a °. 



The measure for oceanic distances is the complement of 

 24°=66°. 



The ratio of land to water is as 100 : 275. 



The ratio of 24° to 66° :: 100 : 275. 



All measurements are to be estimated at the equator. 



The above general law may, for the purpose of demon- 

 stration, be subdivided. 



I. — First subdivision or section of the law. — Many longi- 

 tudinal elevations and depressions on the earth's surface, 

 especially near the greatest median, north and south, ex- 

 tension of each continent, coincide with some meridian. 

 Although this is partly due to early cooling and shrinkage, 

 probably all continents have been extended north and 

 south by successive depositions, as great river-deltas are 

 usually found near the southern terminus of that median 

 line. On these median lines we seldom find volcanoes. 



Demonstration. — As the details regarding North America 

 are most familiar, illustrations will be taken chiefly from 

 that continent, although the law applies as well to all the 

 others. In North America the greatest elongation is about 

 in long. 96° W. of Gr. Near that line, as we shall see later, 

 are found the foci of land forming for our continent, and 

 not far distant the great rivers which drain the Mississippi 

 valley. From Boothia Felix to the Gulf of Mexico we have 

 no volcanoes, and the only earthquake action (near New 

 Madrid, etc.) is due to a great circle of force crossing diag- 

 onally as shown subsequently. 



II. — Second Subdivision of the Law. — Although the median 

 lines of continents run north and south, the outlines or 

 trends of continents form, with the meridians, angles of 

 about 23^° (as I pointed out in " Key to the Geology of the 



* Former State Geologist of Indiana, and for fifteen years Professor of 

 Natural Science in the Indiana State University. 



