Pe ae SA ee eee, ee A Eee 
Se en ee a a ee See Rem gis ew IRR Ae Ir ea ne 
Physics. 391 
oe but its electromotive force is found to change with the 
d also to undergo modifications when the cell is 
short. cireuited, A Daniell cell stably prepared can be made to 
give an electromotive force of about one volt; but in the form of . 
cell in which a porous cup is emplo sa diffusion is apg apa 
going on and thus modifying the electromotive for A water 
battery is generally employed to charge the ace of an elec- 
trometer but the electromotive force of such an element oe 
after a short interval. Beetz found the electromotive force 
zinc copper element filled with spring water to be 0°992 vols 
On examining ag cells of his water battery whieh, had been 
standing a year, he found the follo ning. Nise a of potential 
0°838, 0°678, 0° 734, giving a mean of 0°743 volt. Beetz proposes 
the fo llowing new form of cell for Hots sale electromotive force: 
“Fine alabaster plaster of Paris is mixed with concentrated rd 
phate of copper solution to about the spnaievency em mployed i 
copper wire was asa peat into the copper ae tone it ad 
set, and a zine wire into the zine paste. he upper part of each 
eg was cleared from plaster and tilled up with paraffine.” Thi 
der Physik und Chemie, No. "t, 1884, pp. 402-4 
4. Wave-lengths in the Infra-r ed portion of the solar spectrin, 
—The method of phosphorescence used by ri Beeque 
bles one to see at a glance the whole region ens is es Be inves- 
tigation, and Becquerel claims that the method allows pes 
observer to explore the region further than by means of phot 
graphy, and in this respect is not exceeded by the bolometer or 
thermopile. With a very sensitive phosphorescent agent the 
details of the infra: red region can be observe d by the oe 
he. 
hot s punilassars The slit was ge Sade narrow to enable one 
: e 
oo one could obtain their w een Si A tab oe 
a 
lengths is appended to the author’s paper— C a a Rena 
Sept. 1, 1884, pp. 418-420. 7. 
