aporate, or to be leached out by the rain.

Thirty years ago I saw a quantity of Peruvian guano that contained more
than 18 per cent of nitrogen. It was remarkably light colored. You know
that the white part of hen-droppings consists principally of uric acid,
which contains about 33 per cent of nitrogen.

For many years it was not difficult to find guano containing 13 per cent
of nitrogen, and genuine Peruvian guano was the cheapest and best source
of available nitrogen. But latterly, not only has the price been
advanced, but the quality of the guano has deteriorated. It has
contained less nitrogen and more phosphoric acid. See the Chapter on
"Value of Fertilizers," Page 324.

SALTS OF AMMONIA AND NITRATE OF SODA.

"I wish," said the Deacon, "you would tell us something about the
'ammonia-salts' and nitrate of soda so long used in Lawes and Gilbert's
experiments. I have never seen any of them."

"You could not invest a little money to better advantage than to send
for a few bags of sulphate of ammonia and nitrate of soda. You would
then see what they are, and would learn more by using them, than I can
tell you in a month. You use them just as you would common salt. As a
rule, the better plan is to sow them broadcast, and it is important to
distribute them evenly. In sowing common salt, if you drop a handful in
a place, it will kill the plants. And so it is with nitrate of soda or
sulphate of ammonia. Two or three pounds on a square rod will do good,
but if you put half of it on a square yard, it will burn up the crop,
and the other half will be applied in such a small quantity that you
will see but little effect, and will conclude that it is a humbug.
Judging from over thirty years' experience, I am safe in saying that not
one man in ten can be trusted to sow these manures. They should be sown
with as much care as you sow grass or clover-seed."

"The best plan," said the Doctor, "is to mix them with sifted
coal-ashes, or with gypsum, or sifted earth."

"Perhaps so," said I, "though there is nothing gained by mixing earth or
ashes with them, except in securing a more even distribution. And if I
was going to sow them myself, I would much prefer sowing them unmixed.
Any man who can sow wheat or barley can sow sulphate of ammonia or
nitrate of soda."

"Lawes and Gilbert," said the Deacon, "used sulphate and muriate of
ammonia, and in one or two instances the carbonate of ammonia. Which is
the best?"

"The one t