274 REPORTS ON INVESTIGATIONS AND PROJECTS. 



forces are small. Particularly interesting results were obtained when the 

 hydrometer was a very thin, straight, aluminum tube, at right angles to the 

 light aluminum plate of the condenser. It is shown that for a difference of 

 potential of the disks (supposed horizontal), not too large, there is a stable 

 and unstable position of the movable disk, the former below the latter. The 

 disk, therefore, rises from its fiducial position in the uncharged condenser 

 to a definite height. As the difference of potential increases this height in- 

 creases until at a transitional height both stable and unstable positions coin- 

 cide. For greater differences of potential the disk passes without interrup- 

 tion from the lower plate (guard ring) to the upper plate of the condenser. 

 If the difference of potential is constant the same phenomena may be evoked 

 on diminishing the distance apart of plates of the condenser, by lowering the 

 upper plate on a micrometer screw. Potentials may then be absolutely meas- 

 ured in terms of the distance apart of the plates, at which the continuous rise 

 of the disk first occurs. 



Similar experiments, such as the treatment of Coulomb's law when one of 

 the repelling bodies is a Cartesian diver, the repetition of Mayer's experi- 

 ments when the charged metallic bodies are floated in oil in a charged guard 

 ring, etc., were devised. 



Finally, the experience gained in Chapter III of the report, in relation to 

 methods of filling the diver with a gas in an environment of the same gas, a 

 condition rigorously necessary if the gases are to remain adequately pure for 

 diffusion measurements, suggested the repetition of certain of the experi- 

 ments in Chapter II. These are given in Chapter IV, where the diffusion 

 of gases through other liquids and solutions is also treated. 



Howe, Henry M., Columbia University, New York, N. Y. Grant No. 698, 

 allotted December 13, 1910. Determination of the refining temperature 

 of steel. (For previous reports see Year Books Nos. 6-10.) $500 



As explained more fully in Year Book No. 10, p. 234, hypo- and hyper- 

 eutectoid steel respectively give birth progressively to pro-eutectoid ferrite 

 and pro-eutectoid cementite as they cool slowly through the transformation 

 range, say 900 to 725 ° C. These pro-eutectoid components exist in part as 

 a network, i. e., as cell-walls inclosing the allotriomorphic crystals or grains 

 of austenite from which they spring, and in part they remain within those 

 grains. The network structure itself is transient, coming slowly to a maxi- 

 mum distinctness and again breaking up. During the present year the be- 

 havior of these pro-eutectoid constituents has been studied further. Though 

 the actual precipitation of both ferrite and cementite is probably very rapid, 

 their coalescence into readily visible masses has been found to be unexpect- 

 edly slow, and that of ferrite slower within the transformation range than 

 below it, a fact referable to the greater quantity of ferrite present in the 

 latter case. At 750 the ferrite network of a steel of 0.40 per cent of carbon 



