deposit of metal, instead of forming in a thin,
adherent, and uniform layer, sometimes occurs under the form of
protuberances and crystalline, brittle nodules. When, on the contrary,
the current is very strong, the deposit is pulverulent, that is, in a
confused crystallization or in an amorphous state.

Further along, we shall find an application of this remark. We obtain,
moreover, all the intermediate effects of cohesion, form, and color of
galvanic deposits.

When, into a solution of acetate of lead, we pass a current through
two platinum electrodes, we observe the formation, at the negative
pole, of numerous arborizations of metallic lead that grow under the
observer's eye (Fig. 1). The phenomenon is of a most interesting
character when, by means of solar or electric light, we project these
brilliant vegetations on a screen. One might believe that he was
witness of the rapid growth of a plant (Fig. 2). The same phenomenon
occurs none the less brilliantly with a solution of nitrate of silver.
A large number of saline solutions are adapted to these
decompositions, in which the metal is laid bare under a crystalline
form. Further along we shall see another means of producing analogous
ramifications, without the direct use of the electric current.--_C.
Decharme, in La Lumiere Electrique._

* * * * *

ELECTRIC TIME.

By M. LIPPMANN.

The unit of time universally adopted, the second, undergoes only very
slow secular variations, and can be determined with a precision and an
ease which compel its employment. Still it is true that the second is
an arbitrary and a variable unit--arbitrary, in as far as it has no
relation with the properties of matter, with physical constants;
variable, since the duration of the diurnal movement undergoes causes
of secular perturbation, some of which, such as the friction of the
tides, are not as yet calculable.

We may ask if it is possible to define an absolutely invariable unit
of time; it would be desirable to determine with sufficient precision,
if only once in a century, the relation of the second to such a unit,
so that we might verify the variations of the second indirectly and
independently of any astronomical hypothesis.

Now, the study of certain electrical phenomena furnishes a unit of
time which is absolutely invariable, as this magnitude is a specific
constant. Let us consider a conductive substance which may always be
found ident