October 19,1882.] JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
361 
than those they occupied; and “ repotting ” is turning plants out 
of their pots, reducing their balls, and placing them in the same or 
similar pots. When plants are potted enough room shou d be left 
in the pots as will hold as much water as will thoroughly saturate 
the soil contained in them. A quarter of an inch is enough to 
leave in a 3-inch pot, half an inch in a 4|-inch pot, 1 inch in a 
6-inch pot, and 2 inches in a 10-inch pot, and so on.—N. B. 
THE MANURIAL VALUE OF PHOSPHATE OF 
MAGNESIA. 
In my first letter on the manurial value of phosphate of mag¬ 
nesia (page 290) I said that the point mainly regarded by chemists 
in assigning values to different combinations of phosphoric acid 
was their solubility in, water. With this quality their diffusibility 
through the soil is manifestly intimately connected, for on their 
diffusibility the activity of fertilisers ultimately depends. The 
solubility of a phosphatic material is largely promoted by fineness 
of division, and so also is the completeness with which it can be 
intermixed with the soil whilst it remains a powder, or distributed 
thoroughly through the soil afterwards when brought into solution. 
Generally speaking, therefore, in respect of manures, we may con¬ 
sider solubility and diffusibility as expressing the same quality 
in them ; but this is not always true. If perfectly soluble acid 
phosphate of lime be added to a chalk soil the phosphoric acid 
undergoes immediate neutralisation, and is fixed in the mere upper 
crust of the ground. Diffusion is thus checked until this crust 
is saturated with phosphoric acid, when the process of diffusion 
may again go on and carry some of the phosphate a little deeper 
in the soil, and so forth. On the other hand, when the soil is a 
clay deficient in lime the perfectly soluble phosphate may sink 
below the reach of the roots of plants before it is physically 
fixed in the manner explained by Liebig to be necessary, as quoted 
in my last letter, page 341. 
It is manifest, therefore, as it seems to me, that there must be 
a degree of solubility between that of the so-called insoluble phos¬ 
phates and the perfectly soluble acid phosphate of lime, better 
calculated than either of these two extremes for diffusion through 
soils in general, and such a compound, I believe, we have, as I 
hinted in a former letter, in phosphate of magnesia. Voelcker 
ascertained (see table of solubilities, page 190), that a gallon of 
distilled water dissolved about 0 56 grain of a specimen of Cam¬ 
bridge coprolite, and that when 1 per cent, of sal ammoniac was 
added to the water 152 grains were dissolved per gallon. Of 
Suffolk coprolites, soluble to the extent of 0 56 grain per gallon, 
he found that when a per cent, of sal ammoniac was added to the 
water the solubility rose to 1T2 grains. Roughly speaking, there¬ 
fore, we may say that the solubility of coprolites is more than 
doubled by the addition of the sal ammoniac ; but Voelcker con¬ 
cluded that neither nitrate of soda nor common salt materially 
modified the solubility of phosphate of lime, a conclusion opposed 
to the general opinions of chemists as well as to that of Liebig. 
Jamieson states that the solubility of coprolites finely ground is in 
water, 113 grains ; in nitrate of soda, T33 grains ; in sulphate of 
ammonia, 146 grains ; whilst Liebig found that in the case of water 
with one part of sulphate of ammonia in 540 parts by weight of 
water one gallon dissolved 4'4 grains of tribasic phosphate of lime : 
with one part of common salt in 500 of water one gallon dissolved 
2-2 grains ; and with one part of nitrate of soda in 333 of water 
one gallon dissolved 2 5 grains. It will be readily understood 
that owing to differences in the mechanical state of aggregation 
of the particles of phosphate of lime, and in the strength of the 
solution, identical results could not reasonably be expected even 
if the errors of manipulation which necessarily affect such deter¬ 
minations could be eliminated, but the following points may be 
considered to be satisfactorily proved. 
1st, A very slight degree of solubility in water will enable a 
phosphate of lime to feed plants with phosphoric acid. 
2nd, The slight degree of solubility possessed by phosphate of 
lime is considerably increased when sal ammoniac or sulphate 
of ammonia, even in very minute quantities, is added to distilled 
water. Carbonic acid solution produces similar results in the 
solubility of phosphatic materials. This point is so well under¬ 
stood that it will not be disputed. Phosphate of lime is also 
soluble, in no inconsiderable quantities, in liquids which contain in 
solution various organic non-acid substances, and when recently 
precipitated it is readily soluble in carbonic acid. A saturated 
solution of carbonic acid will dissolve fifty-two grains per gallon 
of bone phosphate, whereas distilled water will dissolve only 
54 grains of it.—( Lassaigne Ann. Ch. et PTuys. (3.) 25.348; and 
Vodclter , “ Solubility of Phosphatic Materials,” p. 10.) I may 
here state that freshly precipitated phosphate of lime was found 
by Voelcker to be dissolved by distilled water in the proportion 
of 5 66 grains per gallon ; but when this bad mixed with it a 
per cent, only of sal ammoniac the solubility was increased to 
21-7 grains, or fourfold. 
It is, therefore, evident that chemists ought to make some 
allowance for the increased value of phosphates when organic 
matter yielding carbonic acid on decomposition, or salts of am¬ 
monia, are mixed with the manure ; but on the present system of 
valuation nothing whatever is allowed for organic matter, though 
formerly a different system prevailed, £1 per ton being allowed 
for it : this is little enough. No additional value is given for 
phosphoric acid when associated with ammoniacal salts, though 
its value is so much increased by their action. Voelcker says in 
this paper on the solubility of phosphatic materials, “The various 
conditions which affect the solubility of lime in water, therefore, 
have a direct practical bearing on the application of bone manures 
in agriculture ; ” has not Jamieson shown incontestably that this 
observation may be extended with truth to coprolites, if not to 
even less soluble mineral phosphates?— Inquirer. 
AMATEUR'S VINERY". 
I WANT a small cheap house in which I can grow Grapes and 
also a few plants, some of them rather tall, such as Palms and 
Ferns, therefore the stage must not be made on the orthodox plan 
for having the plants “close to the glass.” Can you throw out an 
idea that will help me in this matter ? I think I have seen some¬ 
thing of the kind in the Journal, but have been too negligent to 
preserve all the numbers. I am an attentive reader, nevertheless, 
and shall appreciate whatever assistance it is in your power and 
disposition to render in this matter.—J. P. Bousfield. 
[Mr. Luckhurst’s “idea” may possibly be of service in this 
case ; but he broaches it with the condemnation of “ cheap houses, 
because they are not durable,” and observes—“The accompanying 
Fig. 58. 
figure is a section of a light, strong, and durable vinery suitable 
for any garden, but peculiarly adapted to the requirements of an 
amateur by the arrangement of the interior. The roof is a fixture ; 
air given as shown. Its dimensions are :—Height of back wall 
from floor, 9 feet 6 inches ; apex of roof from floor line, 12 feet; 
height of the front wall from the bottom of the Vine border, 2 feet 
8 inches ; height of the glazed part of the front, 4 feet 6 inches ; 
width, 16 feet; extreme height of stage, 3 feet; width of stage, 
5 feet; the interior retaining wall is 44- inches, or a single brick 
in thickness. The iron pillars require to be placed about 10 feet 
apart, and an iron bar passing along under the roof from pillar to 
pillar imparts great strength to it. The whole surface of the 
floor should be paved or concreted and faced with Portland 
cement. The Vines should be planted in the narrow interior 
border, the roots passing through arches to the outside.” 
HARDY PERENNIALS FOR MASSING —A PLEA FOR 
A BETTER NOMENCLATURE. 
There is no doubt that hardy perennials, or, as they are 
generally called, “ herbaceous plants ” (from the fact of some of 
them being herbaceous), are still slowly gaining favour. The 
singular beauty of some of them, their great adaptability for 
supplying cut flowers, and the amount of admiration lavished 
on them by people of taste when the plants happen to be placed 
in telling positions, is gradually forcing some persons who 
have hitherto tried to ignore them to now learn some of their 
long ugly names, and to cultivate a few of the more showy 
