378 CARNEGIE INSTITUTION OF WASHINGTON. 



of hardness caused by tensile rupture in low-carbon steel of 0.11 per 

 cent of carbon is isotropic, within the limits of observational error. 



2. Pearlite Divorce and Related Subjects. 



The study of the divorcing of the carbon-iron eutectoid pearlite 

 has been pursued. Though divorce is the more rapid the larger the 

 quantity of the free or pro-eutectoid element present, yet it occurs, 

 though slowly, even in the complete absence of this element. It is 

 opposed by either long or high prior heating. It is promoted and 

 opposed by minor causes difficult to detect, so that the degree of divorce 

 varies greatly between adjoining areas in any given specimen. Divorce 

 softens and ductilizes the steel, but at a disproportionate loss of maxi- 

 mum and elastic tensile strength. It affects these properties of very 

 low-carbon steel only slightly. It lessens the impact resistance of 

 notched specimens, but this effect is slight in the case of eutectoid and 

 hyper-eutectoid steels. 



The size of the grains of ferrite of an un-overstrained steel increases 

 at temperatures within the transformation range, contrary to general 

 belief. 



The experiments throw doubt on the general belief which connects 

 the Widmanstattian structure with the rate of cooling. They show 

 that the stability of this structure is very great. 



Nichols, E. L., Cornell University, Ithaca, New York. Systematic study of 

 the properties of matter through a wide range of ternperatures. (For previous 

 reports see Year Books Nos. 4-12.) 



For the more complete study of the fluorescence and absorption of the 

 uranyl salts we have had samples of 25 different compounds specially 

 prepared by Mr. G. O. Cragwall, of the Department of Chemistry of 

 Cornell University, with particular attention to the utmost attainable 

 purity. These have been investigated at the temperature of liquid 

 air and their fluorescence spectra photographed by methods already 

 described. 



The spectra are without exception less complex than those obtained 

 from the salts from Kahlbaum previously studied, and in the four 

 instances, i. e., UO2SO4, U02(N03)2, UO2CI2, and UO2 SO4.K2SO4, in 

 which the preparations of Cragwall and those from Kahlbaum were 

 supposed to be of identical composition, we find identity of position as 

 to the more prominent series, but that a bewildering mass of lesser 

 bands are absent in the new samples. 



The photographs of the Cragwall preparations have all been meas- 

 ured, many of them both on the comparator and by projection, and the 

 data are now being studied with a view to possible relations between 

 the frequency intervals and molecular weights; also to determine the 

 effect of physical condition, etc. 



