mi-weekly. Please tell me a process by which I can lengthen
the time. A. Put in three fish, 11/2 inches in length, to one gallon of
water, one small bunch of fresh water plants to one gallon of water.
Tadpoles (after they have cast their branchia or gills), newts, and rock
fish can be used to the extent of six to the gallon. The aquatic plants
will supply the fish with sufficient oxygen, so that the water will
seldom require changing.

(30) A. S. writes: I am about to construct an aqueduct 1,200 feet in
length, the water level differing 40 feet. By placing a forcing pump in
the valley I could then raise the water to a height of 40 feet, and
having erected a tank at that height and connected it by means of pipes
with another tank 1,200 feet distant, but on the same level, the water
according to a law of nature would travel over the distance of 1,200
feet. But finding it very difficult to erect tank 40 feet high, I would
prefer to construct the whole on the incline. Will the forcing pump
having just power enough to raise the water 40 feet perpendicularly into
the tank have sufficient power to force it into a tank of the same
elevation through 1,200 feet of pipe running on the incline, or must I
have more power, and how much more? A. The forcing pump must have enough
more power to overcome its own additional friction and the friction of
water in the long inclined pipe. Allow 20 per cent more power at least.

* * * * *

MINERALS, ETC.--Specimens have been received from the following
correspondents, and examined, with the results stated:

Box marked C. H. (no letter.)--1. and 2. Garnetiferous quartz rock. 3
and 4. Micaceous quartz rock. 5. Granite. 6. Basalt with traces of
chalcopyrite.--L. C. G.--They are fossil sharks' teeth, common in marl
beds.--J. E. C.--1. Iron sulphide and lead sulphide. 2. Quartzite, with
traces of galena and molybdic sulphide. 3 and 4. Dolomite. 5.
Fossiliferous argillaceous limestone, containing traces of lead
sulphide. 6. Lead sulphide in argillite.--C. T. M.--1. A silicious
kaolin. 2. Similar to No. 1. Useful if mixed with finer clay for white
ware. 3. Silicions carbonate of lime--some of this would probably make
fair cement. 4. Brick--the clay from which this was made would probably
be useful to potters. 5 and 6 are very silicious clays.

* * * * *

COMMUNICATIONS RECEIVED.

Liniment. By J. L. T.

Seen and Tangible