408 Scientific Intelligence. 
12. Density of the Halogens at very high temperatures.——Profes- 
sor Crarts has repeated the experiments of the Messrs. Meyer, 
with certain modifications, and finds with them that the density 
of iodine vapor at the temperature obtained with the gas furnace 
of Perrot is two-thirds of the normal density, although he thinks 
their estimates of the temperature too high. In experimenting, 
however, with free chlorine he obtained values corresponding to 
the normal density of Cl.,. 
More recently Victor Meyer has published additional experi 
ments on the same subject, which indicate that while chlorine 
does not assume the abnormal condition corresponding to 3Cl, be- 
low 1200 degrees, iodine vapor passes into a similar state at 1000 
degrees. He confirms also the results of Crafts in regard to the 
density of chlorine gas, which had been previously prepared and 
i i finding that under these 
circumstances the density corresponded approximately to Cl, at 
the same temperature at which the chlorine formed in the flask 
two states of density corresponds to the difference between oxy- 
gen gas and ozone at the ordinary temperature of the air. Vic 
ously only preliminary notices of an investigation still in pros 
ress. The idea that a chemical decomposition or dissociation has 
. pee S60 
tained, and the anomalous densities observed, so far as bie fe 
nown. Me 
13. Use of the Heliotrope for telegraphic purposes in triangula- 
tion. Letter to J. D. Dana, from Capt. C. P. Parriaso®, Super 
intendent of the Coast Survey, dated Washington, Mar. 26, 1 
—Having noticed in Nature several references to the use 0 
sun for telegraphic purposes, I beg to say that the heliotrope—* 
