trouble has been experienced in gravity
cells due to the creeping of the salts over the edge of the jar.
Frequently the upper edges of the jars are coated by dipping in hot
paraffin wax in the hope of preventing this. Sometimes oil is poured
on top of the fluid in the jar to prevent the creeping of the salts
and the evaporation of the electrolyte. The following account of
experiments performed by Mr. William Reid, of Chicago, throws light on
the relative advantages of these and other methods of preventing
creeping.

The experiment was made with gravity cells having 5-inch by
7-inch glass jars. Four cells were made up and operated in a
rather dry, warm place, although perhaps under no more severe
local conditions than would be found in most telephone exchanges.
Cell No. 1 was a plain cell as ordinarily used. Cell No. 2 had
the top of the rim of the jar treated with paraffin wax by
dipping the rim to about one inch in depth in melted paraffin
wax. Cell No. 3 had melted paraffin wax poured over the surface
of the liquid forming a seal about 3/16 inch in thickness. After
cooling, a few small holes were bored through the seal to let
gases escape. Cell No. 4 had a layer of heavy paraffin oil nearly
1/2 inch in thickness (about 6 oz. being used) on top of the
solutions.

These cells were all run on a load of .22 to .29 amperes for
15-1/2 hours per day for thirty days, after which the following
results were noted:

(_a_) The plain cell, or cell No. 1, had to have 26 ounces of
water added to it to replace that which had evaporated. The
creeping of zinc sulphate salts was very bad.

(_b_) The waxed rim cell, or cell No. 2, evaporated 26 ounces of
water and the creeping of zinc sulphate salts was not prevented
by the waxed rim. The wax proved of no value.

(_c_) The wax sealed cell, or cell No. 3, showed practically no
evaporation and only very slight creeping of zinc sulphate salts.
The creeping of salts that took place was only around spots where
the edges of the seal were loose from the jar.

(_d_) The paraffin oil sealed cell, or cell No. 4, showed no
evaporation and no creeping of salts.

It was concluded by Mr. Reid from the above experiments that the wax
applied to the rim of the jar is totally ineffective and has no
merits. The wax seal loosens around the edges and does not t