other by detaching a counterweight closes a cock and stops the supply of
water altogether.

It will be seen that these instruments are not adapted for shifting about
from place to place in order to observe different temperatures, but rather
for following the variations of temperature at one and the same place. For
many purposes this is of great importance. They have been used with great
success in porcelain furnaces, both at the famous manufactories at Sevres
and at another porcelain works in Limoges. From both these establishments
very favorable reports as to their working have been received.--_W.R.
Browne, in Nature_.

* * * * *

[NATURE.]




THE TEMPERATURE OF THE SOLAR SURFACE.


I have, during the summer solstice of 1884, carried out an experimental
investigation for the purpose of demonstrating the temperature of the
solar surface corresponding with the temperature transmitted to the sun
motor. Referring to the illustrations previously published, it will be
seen that the cylindrical heater of the sun motor, constructed solely for
the purpose of generating steam or expanding air, is not well adapted for
an exact determination of the amount of surface exposed to the action of
the reflected solar rays. It will be perceived on inspection that only