SCIENTIFIC SUMMAKY. 
217 
must also be sucb as would produce those internal molecular displacements 
and those strains which are observed actually to take place in glacier-ice, 
and must therefore be present to every part of the glacier as its weight is, 
but more than thirty-four times as great. 
The Magnetism of Chemical Comhinations. — Herr Wiedemann has laid a 
paper on this difficult problem before the Academy of Berlin. Working on 
the principle that the salts of metals showing magnetic properties possess 
those properties in some degree, Herr Wiedemann has found that “ in all 
the salts of the same metal which are in an analogous combination, the pro- 
duct of the temporary magnetism excited by the magnetic force in the unit 
of weight of the salt by its atomic weight is a constant number ; or, in 
other words, that the magnetism of an isolated atom of one of these salts is 
constant. Salts in the solid state give nearly always the same result, espe- 
cially when they contain water of crystallisation. In case these solid salts 
contain no water of crystallisation, their atomic magnetism is generally a 
little more feeble : this is especially seen in the case of the anhydrous salt 
of copper. The magnetism of the salts of copper is peculiar, especially the 
bromide 5 for here there are two diamagnetic bodies combining to form a 
magnetic compound.” 
Temperature and Refraction. — The importance of considering the relation 
between these two conditions was well shown in a paper addressed to the 
French Academy quite recently by M. Faye, who has been writing on the 
subject of astronomical errors of observation in this paper. M. Faye said 
that, with the astronomical instruments of Gambey, we obtained not only 
an immediate estimate of seconds, but even of the tenths of seconds 5 and it 
is, he observed, by seconds that the errors of observations are to be recorded, 
especially observations by reflexions in the mercury bath. M. Faye, in 
trying to discover the causes of errors (not merely due to personal observa- 
tions), thinks he has discovered them in the very imperfect manner in 
which the corrections for refraction are made. In the observatory of Green- 
wich, for example, he said, the external temperature is considered, but not 
the temperature of the room in which the observations are being conducted j 
this, he said, was a most fertile source of error. — Vide Comptes-Rendus, 
March 8. 
What is meant hy the term Catharismf ” — At a recent meeting of the 
Chemical Society of London, Mr. Charles Tomlinson explained the sense in 
which he applied the new term catharism ” (from tcadapSs, pure or clean') j 
distinguishing between clean ” in its ordinary and in its chemical sense. 
The finger could not be made chemically clean by any process, whereas a 
glass rod, cleansed with strong acids or alkalies, and well washed, was 
chemically clean, and no longer possessed the power of liberating either salt 
or vapour from liquids. The action of solid bodies in determinating these 
changes he ascribed to the greasy film which, after exposure to the air, they 
are sure to acquire. For this film, the adhesion of the solid or vapoiu’ is 
greater than it is for the glass, and hence the effect of the solid. To such 
chemical uncleanness all phenomena of this kind should, he thought, be 
ascribed, and he defined a nucleus as a body which has a stronger adhesion 
for the gas, or the salt, or the vapour of a solution, than for the liquid 
which holds it in solution.” He repudiated the notion that temperatme has 
