DECEMBER 8, 1899. ] 
he estimates that these ions are molecular 
aggregates of about 8000 ordinary molecules 
each. This estimate of the mass of the ions is, 
of course, based upon data not altogether satis- 
factory. 
THE RESPIRATION CALORIMETER AT MIDDLE- 
TOWN, CONN. 
PROFESSORS ATWATER AND ROSA give, in 
the Physical Review for September and October, 
a very complete description of the calorimeter 
chamber which they are using at Middletown 
in their interesting experiments upon energy 
transformations in the human body. 
THE COMPENSATED ALTERNATOR. 
THE alternating current dynamo, when used 
to supply current to lamps only, or to one type 
of electric motors only, may be made to give 
constant electromotive force by providing a 
compound field winding. -When, however, an 
alternator supplies current in varying amounts 
to lamps and to motors simultaneously, the 
electromotive force cannot be kept constant by 
compounding. One of the most interesting of 
recent improvements in the alternator is that of 
E. W. Rice, Jr., of the General Electric Com- 
pany. The alternator and exciter are mounted 
on the same shaft, and the alternating currents 
pass through the exciter armature on their way 
to the mains, causing such variations of the 
electromotive force of the exciter as to compen- 
sate for all kinds of variations of load on the 
alternator. This new alternator is described 
in the American Electrician for November. 
AWG Sb 186 
NOTES ON INORGANIC CHEMISTRY. 
A PAPER has been lately issued by the Wis- 
consin Academy on the influence of the presence 
of pure metals upon plants, by E. B. Copeland 
and L. Kahlenberg. It is a complete refu- 
tation of the theory of Nageli of the oligo- 
dynamic effects of metals upon plants, which 
is that where a plant is growing in water, in 
contact with a metal as copper, a trace of cop- 
per goes into the solution as a metal and pro- 
duces a toxic action very different from that 
produced by a salt of copper in solution. In 
the experimental portion of the work of Cope- 
‘SCIENCE. 
861 
land and Kahlenberg, plants (corn, oats, lupines 
and soja beans) were grown in water in paraffin 
coated glass beakers, in which were exposed as 
nearly as possible the same surfaces of different 
metals. Twenty-five or more elements were 
tested, and while at the end of the experiment 
many of them were scarcely tarnished, most 
showed themselves to have had some influence 
upon the plant used. Comparing with the se- 
quence given by Neumann of elements arranged 
according to their surface tensions—magnesium, 
aluminum, manganese, zinc, cadmium, thallium, 
iron, cobalt, nickel, lead, hydrogen, bismuth, 
arsenic, antimony, tin, copper, mercury, silver, 
palladium, platinum, gold—all of these ele- 
ments down to mercury, except aluminum, 
tin and magnesium, are injurious, and except- 
ing further manganese and bismuth, fatal dur- 
ing the time of the experiment. Mercury and 
silver were sometimes injurious, palladium, 
platinum and goldnever. Regarding aluminum 
and magnesium, their salts are comparatively 
harmless. Comparing their results with the 
known toxicity of the salts of the correspond- 
ing metals, the authors conclude that the poison- 
ous action is due to the solution of the metal in 
the form of a salt and not to an action of any 
other nature. The paper gives an interesting 
summary of our knowledge on the toxicity of 
metals toward plants, and has also a bibliog- 
raphy of the subject. 
IN a paper on the heat of combination of cop- 
per with zinc, presented to the Chemical So- 
ciety (London), Dr. T. J. Baker makes use of 
chlorin water and of HNO,, 3H,O as solvents of 
the brass. Up to 30% copper no heat of forma- 
tion could be detected ; it then begins and rises 
to an ill-defined maximum at 62% copper, and 
then gradually sinks to zero at 100% cop- 
per. This alloy of 62% copper, while pos- 
sessed of somewhat remarkable properties, 
does not correspond to any simple atomic com- 
pound (Cu;Zn; = 61.8% copper) ; the existence 
of the supposed compound CuZn,(= 32.6% 
copper) is rendered doubtful from the fact that 
the alloy of this proportion shows almost no 
heat of formation. 
FURTHER researches on radiant matter in 
pitch-blende have been made by A. DeBierne, 
