4 EDWARD WILLIAMS MORLEY— CLARKE aumum t ^SK 



In 1878 Morley began the series of investigations that made him famous. His attention 

 had already been drawn to the fact that the proportions of oxygen in air were not absolutely 

 constant, but subject to slight variations. What do these variations mean? That is the 

 question that Morley sought to answer, at least in part, and his task was one of extreme dehcacy. 

 The solution of the problem involved the construction of elaborate eudiometric apparatus, 

 with which the probable error of a determination of oxygen in air was not more than one four- 

 hundredth of 1 per cent. The results of his investigation appeared in 10 separate papers, 

 published between the years 1879 and 1S82, three years of labor. 



On one side Morley's problem was meteorological. Professor Loomis, of Yale College, 

 had put forth the hypothesis that so-called "cold waves," those severe and sudden falls in the 

 temperature of the air, were not due to horizontal currents moving from the north southward 

 but to the descent of air from high elevations at times of high barometric pressure. The upper 

 layers of the atmosphere were poorer in the relatively heavier oxygen than the lower layers 

 near the surface of the earth. Hence, if the Loomis hypothesis is correct, the air collected during 

 a cold wave should show a deficiency of oxygen. 



Morley had already made analyses of air from different localities, and in 1880, during 110 

 consecutive days, he made analyses of the air at Hudson. Each determination of oxygen was 

 made on the day that the sample of air was taken. To quote Morley's own words: 



The theory that the deficiencies of oxygen in the atmosphere are caused by the descent of air from an eleva- 

 tion fairly well agrees with the facts. 



This cautious statement shows the scrupulous honesty of the man. A more positive 

 assertion would have been justifiable. 



An attempt to trace the workings of another man's mind would of course be rather pre- 

 sumptuous. To do that is the privilege of the novelist, who can create imaginary characters. 

 It seems highly probable, however, that Morley's research upon the composition of air had 

 much in it to suggest his next and most famous investigation on the composition of water; 

 that is, on the relative atomic weights of oxygen and hydrogen. The transition from one 

 research to the other was quite natural. An intermediate step was the determination of the 

 amount of moisture retained by gases after drying by means of sulphuric acid, or over phosphorus 

 pentoxide, for that was an essential preliminary to his work on the composition of water by 

 volume; a study of the proportions by volume in which the two gases, oxygen and hydrogen, 

 combine. The volume relations and the weight relations are not the same. In the determina- 

 tion of gaseous densities the first relation is needed as a small correction to the other. 



Morley's work on the atomic weight of oxygen, that of hydrogen being taken as unity, 

 covered a period of 11 years. Much time was spent in the detection of constant errors, and in 

 making "assurance doubly sure" as to the purity of his materials. No precaution was over- 

 looked, for the highest possible accuracy was his aim. 



The determinations of atomic weight were made by two distinct methods. First, he effected 

 the direct synthesis of water from weighed quantities of its component elements. The hydrogen 

 was weighed as occluded in palladium, 600 grams of that metal being used. Secondly, he deter- 

 mined the density of the two gases, using the correction mentioned in the preceding paragraph. 

 The results obtained checked each other within the admissible range of experimental uncertainty, 

 and later determinations by other chemists have differed but slightly from Morley's. His final 

 value for the atomic weight of oxygen was 15.879. The outstanding uncertainty is probably not 

 much greater than 1 part in 10,000. 



It is evident that this research of Morley's upon atomic weights was quite as much physical 

 as chemical. Even while he was engaged upon it he found time to cooperate with others in some 

 purely physical investigations. He worked with A. A. Michelson in the famous attempt to 

 determine the relative motion of the earth and the luminiferous ether, and also upon the possibility 

 of establishing a fight wave as an absolute standard of length. With H. T. Eddy, and afterwards 

 with D. C. Miller, he studied the velocity of fight in a magnetic field. Witfi Miller he also 

 investigated the thermal expansion of air, nitrogen, and carbon dioxide. In connection with the 

 latter research Morley constructed a new form of manometer by which differences of pressure as 

 small as one ten-thousandth of a millimeter could be measured. With W. A. Rogers he studied 

 the expansion of metals by the interferential method; and with C. F. Brush the conduction of heat 



