Proceedings of the Polytechnic Association. 885 



Carbon Separated from Different Combinations. 

 M. Berthelot, of Paris, has communicated to the Comptes Eendus 

 a paper " on the immediate analysis of different varieties of carbon," 

 in which he describes the influence, upon varieties of carbon already 

 formed, of sundry agents, such as heat, chlorine, iodine, oxygen, and 

 electricity, also the characteristics of carbon extracted from the 

 various compounds. He states as the result of his experiments and 

 observations on the latter subject, that carbon when separated from 

 compounds containing hydrogen, takes the condition of amorphous 

 carbon ; while that derived from its combinations with chlorine, sul- 

 phur, boron, andped'haps oxygen, inclines to the state of graphitic 

 carbon, that is, carbon which can furnish graphitic oxj-d. Amorphous 

 and graphitic carbons would therefore appear to represent, not 

 different conditions of carbon itself, but certain polymeric states cor- 

 responding with that element. 



The Variability of Personal Equation. 

 The interval of time which intervenes between the actual and the 

 observed transit of a star, called the personal equation, varies with 

 every individual observer, and is one of the most uncertain elements 

 in chronographic determinations of longitude. It has generally been 

 assumed that the value of this function of time is the same during 

 an entire series of observations. Mr. William A. Rogers, Director 

 of the University at Alfred, ^N". Y., has endeavored to ascertain 

 wdiether the power of perceiving and recording does not vary in the 

 same observer under different conditions, and has given the result of 

 his investigations in the American Journal of Science, No. 141, in a 

 paper "On the Variability of Personal Equation in Transit Observa- 

 tions." He gives a summary of about 8,000 observations of artificial 

 stars, made of paper and centered uj)on fine steel w'ires placed in a 

 vertical position, and so connected with a Bond Chronograph that, 

 by means of electricity, the exact time of opposition was automati- 

 cally recorded. By using this automatic record as a standard with 

 which the observed time of passage could be compared, Mr. Rogers, 

 Prof. E. M. Tomlinson, and Mr. H. E. Babcock, each made a series 

 of observations from which it was determined that, 1.' The personal 

 equation is a vaiying quantity. 2. The probable error of observation 

 is less for an abnormal than for a normal position of the body, which 

 is contrary to what would seem a natural inference. 3. An exhausted 

 state of tlie system produced a sliglitly favorable result in diminish- 



