596 
THE GARDENERS' 
CHRONICLE. 
[Sept. 5, 
experience last year as to the utility of chlorine as | 
a preservative agent ? The subject is likely to be | 
evived. 
——— 
POLMAISE HEATING. 
Ir was not my intention to have trespassed again so 
soon on your columns ; but, judging from private commu- 
nications, that the subject of Polmaise has new interest 
for your readers, I am anxious that truth should pre- 
vail ; and having, I believe, found her, if not at the 
bottom of the well, at least concealed under the (hot) 
water, I wish she should stand clear, appreciated, and 
acted upon by all. Ina case of the kind now under discus- 
sion, there is always a large number of persons who 
will not believe that anything that is new can be true. 
*€ It’s a nine days wonder ;” “it must fail.” For such 
persons these remarks are not intended; but 
there is another class of persons who (perhaps wisely) 
mistrust anything called new, and express their doubts 
in various ways ; and no orm of exp i 
is “oh this is not new; it’s quite an old plan revived ; 
Mr. So and So tried this and failed !” and this really 
without ever attempting to ascertain whether the two 
plans were identical or not. To such I commend these 
remarks. 
Ti has been stated that Polmaise heating is nothing 
new; that Mr. Penn tried it, and that it completely 
failed ; and that air heating has often been attempted 
and relinquished. The former part of this state- 
ment I believe to be erroneous; the latter part 
correct ; I believe that all other attempts at air heating 
have been made on the following principle :—2 room, a 
church, a factory, or a hothouse was required to be 
heated ; a stove was erected either in the building itself, 
or in an adjoining chamber ; passages or drains were 
made to convey cold air through, or over, or round this 
heated stove ; but such passages or drains were not 
made frora the building itself, which it was desired to 
heat, but from some extraneous source— perhaps, even 
from the external air. It was supposed that the cold 
air would flow over the heated stove, and, having 
warmed itself, would flow into and warm the building. 
Strange mistake, to suppose that we could put more 
into a vessel that was full before! Was it forgotten 
that because we can neither see the air nor handle it, 
that therefore it is material? Was it supposed that, 
while we can only make a. pint measure hold a pint of 
water, we can pour air continually into a room that was 
full of air before? Gases are, doubtless, more com- 
pressible than liquids ; but even to their compression 
there is a speedy limit; the building, to use a plain 
term, becomes choked with air; it can hold no more, 
hot or cold, and the plain fails. Is this Polmaise ? But 
the objector shifts his ground ; he says now—'* Oh, but 
air-heating did answer to a certain extent ; this place 
was heated by it, and that gentleman's faetory warmed, 
but not economically ; and the plan applied to hot- 
houses signally failed in winter." How did it succeed at 
all, if the above view is correct; simply enough : it was 
soon found that if an escape was either provided or al- 
lowed from the upper portion of the building, then warm 
air did flow in, because there was room for it, as 
it went out at one end it came in the other ; but 
mark ! the air that came in was not the same air or any 
portion of that which went out ; the air that went out 
carried with it (perhaps) 60° of calorie; the air that 
came in possibly came in (if from the external air in 
winter) at 20° Fahr., perhaps at 10° Fahr. ; t is had 
to rob the stove of 40° or 50° of heat to bring itself up 
to par, and the next instant fled away with all its store 
of caloric, to be seen no more, to be succeeded by an- 
other current of cold air as exacting as the last, till the 
stove, fairly exhausted of all its heat by the unceasing 
exactions of the icy wind, retired from the contest ; is 
it strange that such a plan was extravagant ? or that 
amidst the frost of winter it totally failed ? but is this 
Polmaise ? 
What would be thought of a man who proposed to 
heat a hothouse by trying to pour hot water into 
a boiler that was full of cold water? Exactly such 
was the attempt to heat a chamber with hot 
air, that was full of cold air, without making 
any provision for its escape. But what should we say, 
were it proposed to heat a building by means of a boiler 
and pipe, a continual stream of cold water being kept 
up into the boiler to become heated, and then allowed 
to run out at the far end of the pipe, never again to 
return to the boiler, but to be succeeded by incessant 
streams of the cold liquid? Exactly similar to this is 
the proposal to heat by hot air, if all the air as heated 
is suffered to escape. Have these been the principles 
of past attempts at air heating, or have they not? If 
they have, it is no matter of astonishment that 
they have failed ; but it is no reason whatever, that 
Polmaise should fail too, when it can be shown that a 
fairly powerful stove has been placed in an air-tight and 
non-conducting chamber, that a full provision has been 
made for bringing currents of air from the lowest level 
of the space to be heated, for passing them over the 
heated surface of the stove, and conducting them again 
into the space from which they came. In fact, when 
those conditions have been observed with air which 
have been fulfilled with water, and when this, which is 
Polmaise, has failed, then I may look at the coming 
winter with anxiety; but in the meantime, I hope 
shortly to bring such considerations before your readers 
as will induce them to believe that, if science speaks the 
truth, Polmaise carries with ita compensating principle, 
so that, to à certain extent, the colder the weather the 
better it will act.—D. B. Meek, Holmesdale House. 
ENTOMOLOGY. 
Cnromos ræntorus, (the Ribbon-footed Corn-fly).— 
The Barley crops have suffered so severely during the 
present year from the attacks of maggots, the offspring t 
of this little fly, and the Wheat not having escape 
from this or an allied species, it seems desirable to call 
the attention of agriculturists to the subject. It has 
lately been. recorded in the fifth vol. of the “ Royal 
Agricultural Journal,” that in August, 1841, the Wheat 
in Surrey exhibited the effect of these insects’ opera- 
tions, and that several weeks earlier the Barley had 
been destroyed to a great extent in Lancashire by them, 
I shall therefore confine my remarks to what has oc- 
curred this summer, In the neighbourhood of Mar- 
tham, in Norfolk, it was supposed in July that more 
than half the Barley crop had been destroyed by the 
Chlorops maggots. At the same period a gentleman 
informed me that full two-thirds of the erop was lost at 
Feltham, in Middlesex, some parts of a field being so 
much injured that it could not possibly produce 5 bshls. 
per acre ; and other fields were suffering in a similar 
way. I heard on the 18th July, from Harlow, in Essex, 
that there would not be half a crop of the late sown 
Barley, owing to the inroads of the Chlorops, and it was 
stated that nothing of the kind had been seen there at 
least for the last 35 years. A few days after this, 
another correspondent informed me that in the north 
of Lincolnshire the ears were so injured by the maggots 
that it was believed the Barley in some places was 
destroyed to the extent of 50 per cent. 
interrupted in the middle ; the wings are incumbent in 
repose, longer than the body, transparent, with 
dark nervures, the lower ones faint, and there are 
wo nervures approximating on the dise; 
halteres ,clavate and bright yellow; legs slender 5 
anterior tibiæ blackish at their tips; the tarsi black, 
with the second and third joints whitish, the other tarsi 
with the tips alone black (fig. 6, the cross lines showing 
the natural dimensions). 
It is difficult to devise any means of preventing the 
assaults of these destructive little flies, for until the 
mischief is apparent their presence is not suspected, and 
then it is too late to attempt to destroy the parent fly 5 
likewise when the corn is housed, although the pups 
may remain the flies bave escaped, and probably are 
depositing their eggs in some of the Grasses until the 
autumn-sown corn is in a proper state to be inoculated. 
It appears, however, that Providence has provided æ 
cheek which will more effectually arrest their operati 
than anything that man can do.. I have frequently 
bred two parasitic flies, one named Cælinius niger, 
which lays its eggs in the larvee of the Chlorops, and 
when the maggots hatch, they feed upon and destroy 
them ; the other is the Pteromalus micans, but it is 
not improbable that the larvee of this fly are destined to 
prevent the too rapid increase of the Ceelinius, ‘Those 
who feel interested in this subject will find the species 
figured and described in the 5th vol. of the “ Royal 
Agricultural Journal."— Ruricola. 
HINTS ON THE CULTIVATION OF AUTUMNAL 
RO 
Perpervan and Bourbon Roses should be planted in à 
good mixture of turfy loam and half decomposed ma- 
nure, (at least one wheelbarrow full to each plant) and 
if standards, they should be carefully staked ; the shoots 
The packet of Barley sent from Feltham was exceed- 
ingly reduced in quantity and quality by the Chlorops ; 
the ears were entirely sterile, or deficient in grain on one 
side, a greater or less portion of their length (fig. 2, the 
ear as separated from fig. 1). On examining the straw 
I found it was sound until I arrived at the top joint, 
where a dirty brown channel was visible on one side 
(fig. 1), and it might be traced on the inside by the dis- 
coloration, although it did not actually penetrate through; 
the channel had been eaten by the maggots from this 
joint up to the base of the ear or even farther, often ex- 
tending two inches, and invariably on the side where 
this groove terminated the ear was either altogether 
abortive or there were only five or six grains perfected 
towards the top. Some Egyptian Barley in my garden 
was similarly affected, the ears having entirely perished, 
or one row out of the six was sterile. 
The eggs are, in all probability, laid by the parent fly 
late in the autumn on the Wheat, or early in the spring 
upon the young Barley stem, in which case it may 
be presumed that the little maggot either descends into 
the plume or eats into the heart of the incipient ear ; 
at the period I received this sample the maggots were 
full fed, and most of them had formed pupæ on the 
inside of the sheath enclosing the ear, and close to the 
groove (fig. 4) ; from one of these the Chlorops had 
just hatched, but I bred several about the 25th Julyy 
‘and from the number of empty cases no doubt a much 
greater number of flies had escaped the first fortnight 
of that month. 
The larva is yellowish-white, fleshy, composed of 
many segments, tapering to the head ; the tail is blunt, 
with two small tubercles (fig. 3) ; the pupa is of a 
ferruginous-ochre colour, nearly cylindrical, elliptical ; 
the extremities rounded (fig. 5). The perfect fly is of 
a yellowish colour ; the head is more of an orange tint 
on the crown, with a black triangular spot at the base, 
on which are placed three ocelli in a triangle; the 
antenne are small and black, the two basal joints stout, 
the second orbicular and compressed, having a bristle 
arising on the back, with an elongated joint at the base ; 
the face is concave, with a cavity beneath to receive the 
organs of the mouth ; the eyes are dark, lateral, and 
orbicular ; the thorax is globose-quadrate, with three 
broad strap-shaped slate coloured stripes, the central 
one not reaching the scutel, and the lateral ones not 
extending to the anterior margin. Close to these is a 
black dot, and the breast is also black ; scutel semi- 
orbieular and bright yellow ; abdomen small, oval, 
depressed, composed of five segments, the base black 
under the scutel, with a black oval dot on each side upon 
the first and second segments; there is also sometimes 
a brown line across the base of four of the segments, 
short slender stripe ; on either side of the pleurze isa]. 
require to be shortened in spring to about three eyes, 
either in February or March according to the season } 
during the summer and autumn a plentiful supply o 
liquid manure will be found highly beneficial : we have 
used Brain's concentrated liquid guano, in the propor- 
tion of one table spoonful to a gallon of water, once & 
week, with great success. 
Among the Hybrid Perpetual and Bourbon Roses 
will be found some varieties having a tendency to throw 
up vigorous shoots, showing little or no disposition to 
flower ; these should be carefully removed during the 
summer, leaving such only as are of medium growth; 
these if shortened to six eyes will be found to produce 
abundance of bloom in the autumn. 
In order to insure a high state of cultivation, it will 
be found necessary to stir the surface of the beds annu- 
ally in November, after which they should be covered 
with a good dressing of manure ; decayed linings, from 
a Cucumber or Melon pit, have been found the most 
effieacious for this purpose. 
In some situations, where the Rose beds are much 
exposed to view, it will be requisite to fork in the ma- 
nure at once, as it would. otherwise appear unsightly 5 
in other cases, however, it may be allowed to remain 0D 
the surface until the plants have received their annual 
pruning, as recommended in the first paragraph. 
If the foregoing instructions are carefully attended 
to, the result will amply compensate the extra labour 
bestowed, as a proof of which, we have the pleasure 9 
stating that the autumnal Roses at the Woodlands 
Nursery, are at this late period of the season (October 
27th) in splendid bloom,— William Wood and Son. 
ON THE ORGANIC COMPOUNDS WHICH coN; 
STITUTE THE NUTRITIVE PORTIONS 0 
THE POTATO. 
By the Rev. Prof, HENSLOW. 
(Continued from p. 565.) " 
With the assistance of this diagram, we may readily 
indulge in speculating upon the proportionat uantities 
of carbon for respiration, and of protein for nourish- 
ment, that may be contained in different weights of 
the Commissioners’ Potato ; or we may compare these 
with different weights required in other vegetable OF 
animal substances. For the sake of further illustratioDr 
we will inquire what would be the weights of Potato re- 
quired respectively by a stout man and his delicate wifes 
supposing the former to need 15 oz. of carbon, and the 
latter 5 oz. daily for the purposes of respiration alone 
and we will further consider what those weights shoul 
be, on the supposition that the supply of carbon is to be 
obtained either from the whole of the solid matter, ? 
only from one or two of the ingredients respectively. 
The results of such a calculation are given in the nex 
diagram, which I will pore to explain : 
AR] 
1 5s SUPERFLUOUS 
containedin rin 
and PRrorsiNe 
| raw meat 
flesh 
starch — 
give the weights of Potat a 
furnishing from 5 oz. to 15 o7. 9 ; 
several c hnbiiadons of solid vegetable matters referred 
to, in the second compartment, by the letters (m 
3 
brane), S (starch), G (gluten). The two compartments 
| 
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i 
4 
f 
