290 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. [ September 28, 1882. 
cold wet locality like this, and where a few bright sunny days in 
succession are of rare occurrence.— William Connelly, Leagram. 
WHAT IS THE MANURIAL VALUE OF PHOSPHATE 
OF MAGNESIA? 
In my letter, page 225 of the Journal of Horticulture, I en¬ 
deavoured to show that agricultural chemists did injustice both to 
the buyers and sellers of manures in failing to appraise the mag¬ 
nesia they may contain. In my present communication I propose 
to carry forward my inquiry to the combination of this substance 
with phosphoric acid, which I believe to be the most useful form 
in which the latter can be applied to the soil for the nourishment 
of plants—an opinion which not only conforms with the teachings 
of Liebig, but is, so far as has yet been ascertained, supported by 
practical results. 
In dealing with the question I shall, in the first place, recall to 
the minds of your readers how much uncertainty prevails concern¬ 
ing the efficacy of different forms of phosphoric acid, and that 
their true money worth to the farmer is by no means adequately 
measured by the valuations which the chemist puts upon them. 
I shall next inquire into the principles upon which, having a due 
regard to what is known of pi ant-nutrition and the mode in which 
it is brought about, these valuations should be made. Then 1 
shall try to show that the teachings of science as explained by 
Liebig are fully borne out by practical experience ; and, finally, 
I shall endeavour to persuade horticulturists as well as agricul¬ 
turists that phosphate of magnesia meets all the requirements of 
a plant food in a most admirable manner, and ask your readers, 
if they are unable to show that it is futile, to assist me in my 
endeavours to spread a knowdedge of the accuracy of what I 
advance. It may be assumed with confidence, I believe, that the 
generality of orthodox agricultural chemists fix, roughly speaking, 
the value of mineral phosphate of lime in a manure at a quarter 
the value which is given to it by dissolving it in oil of vitriol, and 
if, after having been brought into solution, the phosphoric acid is 
precipitated as phosphate of lime by an alkali or alkaline earth, 
the worth of this precipitated phosphate of lime is depreciated by 
one-half as compared with the same salt in the soluble condition. 
This practice in valuation is (and as will appear on good 
grounds) departed from by some chemists, who put the value of 
precipitated phosphate of lime as almost, but not quite, equivalent 
to that of phosphate of lime in mineral superphosphates, say at 
seven-eighths of the value of soluble phosphate of lime in super¬ 
phosphates, mineral phosphate untreated by acid being reckoned 
at one-quarter the value only of the soluble phosphate. The so- 
called insoluble phosphates (though not in fact absolutely in¬ 
soluble) in bone or from guano are generally assumed to be of the 
same value as precipitated phosphate, or to differ little from it in 
value. 
Let us now inquire upon what principle these valuations are 
confessedly based, or what chemists have to say in support of 
them. Broadly speaking we may assume that the point regarded 
is mainly if not wholly based on the solubility of the phosphates 
in water. Dr. Voeleker, in a very careful and conscientious paper 
on the “solubility of phosphatic materials,” shows that one gallon 
of distilled water will dissolve the following amounts of phosphate 
of lime from different sources. 
In a gallon. 
Estremedura phosphorite . 0-10 gram. 
Norwegian apatice . 0'-14 „ 
Coprolites (mean of Suffolk and Cambridgeshire) .... 0’62 „ 
Monk’s Island phosphate. LOO „ 
Pure bone ash (from very hard bone). l'I8 grains. 
Pure tribasic phosphate of lime precipitated, burnt,) g-20 
and finely ground.j ” 
Guano . 2 - 52 „ 
Pure tribasic phosphate precipitated and still moist.. 5 56 „ 
The indications afforded by the foregoing results are summed up 
by Yoelcker in the following conclusions. Extracts only are given 
from his table, and I have arranged the conclusions which I have 
selected in the order which seemed best to suit my line of 
argument:— 
“ 7, The phosphates contained in coprolites, apatite, . . . 
Spanish phosphate, and other phosphatic minerals, especially 
when they are hard and crystalline, are very little acted upon by 
water.” 
“ 8, For agricultural purposes phosphatic minerals, as well as 
bone ash, should be treated with a quantity of sulphuric acid 
sufficient to convert the whole of the insoluble phosphates therein 
contained as completely as possible into soluble combinations. It 
is a waste of good raw materials to leave much of the insoluble 
phosphates unacted upon by acid.” 
“9, Insoluble phosphates present in superphosphate or other 
artificial manure have little or no practical value to the farmer.” 
“ 5, Bone ash is not sufficiently soluble in water to be used with 
advantage by itself or mixed with other fertilising matter as a 
manure.” 
“ 6, The earthy phosphates in Peruvian and phosphatic guanos 
still containing a good deal of organic matter or salts of ammonia 
are sufficiently soluble in water to be readily appropriated by 
plants.” 
And in an earlier part of his paper Yoelcker shows that care¬ 
fully prepared, precipitated, and dried phosphate of lime from 
bone phosphates constitutes “ a very valuable fertilising material 
which is readily appropriated by plants.” 
These conclusions by Dr. Voeleker, w'hich were arrived at about 
fifteen years since, would appear, in fact, to give some explanation 
of the results which Jamieson has shown by actual trial in Aber¬ 
deenshire and Sussex (see report of Review on the Experiments of 
the Sussex Association, page 110, Journal of Horticulture) to follow 
fine grinding of the coprolites used for manuring Turnips. With 
ground coprolites the results were as good as were obtained with 
superphosphate. If, then, phosphate of lime in finely ground co¬ 
prolites, with a solubility in water of only 0 62 grains per gallon, 
can produce results but 10 per cent, below wbat follows from an 
application of soluble phosphate—and Dr. Voeleker considers 
(indeed no one disputes it) that phosphate of lime as found in 
guano, with a solubility of but 2 52 grains per gallon, is sufficiently 
soluble in water to be “readily appropriated by plants ”—it ought 
not to astonish us, seeing that a small addition of sal ammoniac 
to the water increases the solubility of precipitated phosphate 
fourfold, that coprolite may become in a manure containing 
ammonia salts, or in a soil capable of yielding other equally or 
more powerful solvents, sufficiently soluble to produce the results 
which Jamieson obtained. But this question of the action of 
other solvents in conjunction with water must be left for my next 
communication. It is a question full of interest.— Inquirer. 
STRIKING EUONYMUSES. 
On page 270 of your last issue “ A. B.” has some remarks under 
Ihis heading which I can fully endorse as being perfectly correct. 
Had he read carefully the whole of my article he would have 
found that I said these plants could be propagated in rooms by 
merely turning over them a tumbler, and by those who possess 
only a poor knowledge of window plants. When the choice 
variegated forms are required in quantity it is not wise to rely 
upon any makeshift system, but to follow judiciously one that is 
likely to lead to success. 
There are many advantages to be gained by placing the cuttings 
in pots, as described on page 210. When the cuttings are callused 
they can be taken into the Conifer house where a little heat is 
always maintained, and thus they will form roots much more 
quickly than in cold frames. This saves valuable time (which 
means money to those who propagate them for sale), and the 
plants are established in pots and growing freely by the time 
“A. B.” would have them rooted. The better variegated forms 
can be planted out from the cutting pots the same as “A. B.” 
subjected his green kinds to ; but it must be remembered the 
choice variegated forms do not grow so rapidly as the green 
varieties, and by establishing the former in pots they make greater 
progress than if planted directly outside. In extensive nurseries 
with which I am acquainted the better forms are kept in pots, 
which ensures their safe removal at any season.—W. Bardney. 
ON PLANTING FRUIT TREES. 
As the planting season will soon arrive preparing the ground 
should be commenced, as after-success depends much on this. If 
the ground is not properly prepared the trees will not do nearly 
so well, besides being a prey to canker and other evils. Some 
judgment must be used as to the stocks the trees are worked on. 
I should never think of planting Apples on the Crab stock in a 
small kitchen garden, as they soon grow out of bounds and shade 
the ground where good vegetables could be grown, and this 
remark may apply to gardens of a larger size. If the place is of 
good extent an orchard should be provided, where Apples on the 
Crab stock are the best to plant for large crops of fruit; but for a 
kitchen garden I should undoubtedly advise planting those trees 
that are worked on the Paradise stock. Have some method, not 
planting in the middle of the vegetable quarters, which spoils the 
appearance of the garden, besides vegetables, and wastes much 
valuable room. I recommend planting by the sides of walks, but 
not if there should be any danger of shading the trees on the 
walls. 
Generally kitchen gardens are square, with a walk across the 
centre each way. That is the place to plant Apple and Pear trees, 
