660 
THE GARDENERS' 
CHRONICLE. 
[Ocr. 3, 
to cubic inches and fifths of cubic inches. Hence 
one inch depth of rain in the gage will be measured 
by 100 inches of the graduated vessel, and 4, th 
inch of rain may be very easily read off." 
A military officer in India employed a yet more 
simple instrument. Its construction could be regu- 
lated, and its indications ascertained, by means of a 
common rule, divided into inches and tenths. The 
space for the reception of the rain was rectangular, 
10 inches by 12; the quantity deposited was 
received into a box 3 inches by 4, being exactly 
4 of the area of the opening at top. These 
dimensions are very useful because they are not 
fractional ; and the areas which they include are 
in decimal proportion; consequently inches and 
tenths of depth in the one is equivalent to tenths È 
and hundreds of an inch in the other. 
Rain gages are frequently constructed with a 
float, to which an index rod is attached, and becomes 
more or less elevated according to the greater or 
less quantity of rain deposited in the cylinder. 
The float should have no more room in the cylinder 
than is necessary for moving up and down with 
ease, and so that the water may readily pass. When 
this is the case evaporation is almost wholly pre- 
vented. Ifthe funnel is made 10 inches square, 
the cylinder may be 3 or 4 inches in diameter ; and 
if 52 oz. 9 grains, avoirdupois, of water, at a tempe- 
rature of 62°, be poured into the gage, the float will 
be raised as much as if yy of an inch of rain had 
fallen. By this means the index rod may be easily 
and correctly graduated to represent tenths of 
inches of rain, and a subdivision of the spaces may 
be readily effected for the hundred parts. 
From what has been stated, any one with a 
little ingenuity may construct a rain-gage, cor- 
reetly, at small expence. Of the practical utility 
of the instrument one example will be sufficient. 
Suppose a south-wall border is 600 feet in length, 
and 15 in breadth, with a dry bottom ; and that the 
trees maintained a healthy loliage, with rain falling 
at the rate of 21 inches per month, say during the 
months of April, May, and June. The area of 
such border, 9000 square feet, will have received in 
the above period no less than 35,055 gallons of 
rain-water. But if it should happen that instead of 
2% inches, the monthly depth of rain should only 
average half an inch, as was the case in the months 
of April, May, and June, in 1844, the deficiency as 
compared with the quantity found to keep the 
trees in good health, will amount to 28,055 gallons, 
or 1122 tubs such as are used by gardeners for 
watering, containing, when as full as can be wheeled, 
about 25 gallons. The weight of the above quan- 
tity is upwards of 125 tons; the raising of this, 
perhaps fromapump at some distance, and conveying, 
and distributing it on the border, must occasion an 
amount of labour and expence, which those on the 
spot can easily calculate from the certain data 
afforded by the rain gage ; and at the-same time 
those also who could otherwise have had no idea 
of the enormous quantity of water required arti- 
ficially in a dry season for such a border as we have 
named, will be made aware of the necessity of 
supplying it. || 
We are happy to observe that Her Maszsry 
has contributed 207, and His Rovar HIGHNESS 
Prince ALBERT, 10/., to the subscription for the 
reliet of the Nurserymen, &c., who suffered by the 
late Hailstorm. We understand that the losses 
are estimated at 15,0007, and that the Committee 
bave only received, at present, about 15007. 
ENTOMOLOGY. 
ERISTALIS TENAX.— There are 16 species of the genus 
Eristalis recorded as inhabiting England, and some of 
them from their buzzing flight, their form and colour, 
so much resemble hive-bees, that it is difficult to con- 
vince many persons they are different; they are, how- 
ever, easily distinguished by the number of their wings, 
bees having four, and flies only two wings. One of the 
most abundant species is the E. tenax, which one sees 
in the summer and autumn extracting honey from Sun- 
flowers, China-asters, Thistles, Dandelions, &e. T 
males frequently hover in the air, vibrating their strong 
wings with a rapidity which renders them invisible, and 
the body of the ‘animal appears to be immovable ‘and 
suspended in the air, until the fly darts off in pursuit of 
a female, and not unusually returns to the same spot. 
The; eggs of E. tenax are dropped upon stagnant 
water, whilst the female is on the wing, and produce 
very extraordinary larvee ; they were extremely numer- 
ous in July and August in a tub which had been filled 
with chamber-wash and had become putrid. Into this 
slugs and snails were thrown, which seemed to be suited 
to the taste of the maggots, for they atached themselves 
to the floating bodies in masses of 20 or 30, I conclude 
to feed upon them. A vast number appeared to die, 
and when others were full grown they ascended 
the inside of the tub, at night probably when it 
was damp, and reached the earth to undergo their 
transformations, I expect those which died had failed in 
Em 
[3 
their attempts to escape, for I frequently saw them 
when the sun was shining and the surface of the tub 
dry, unable to crawl beyond a couple of inches from the 
liquid they inhabited. "The way in whieh they tumble 
about in the water, like porpoises, is very amusing ; 
they dilate their broad sueker-like heads, and shoot out 
two small membranous tubercles beneath ; the tail is 
twisted in every direction, and being, like the body, 
composed of innumerable rings, it can be lengthened or 
contracted at ‘pleasure, and one sees a fine, brown, 
double, hair-like tube down the centre, which projects 
about 1-8th of an inch beyond the membranous and 
stouter tail, the tip of it forms a little mouth or spiracle 
surrounded by six hairs, which rest on the surface of 
the water and supply the animal with air. The under 
side exhibits an infinity of vessels, and a large mass or 
two under the thorax, like a bundle of salmon-coloured 
gs ; there are also seven pair of membranous feet 
surrounded by little hooks, distinctly projecting from 
the ventral segments, which assist the larva in walking. 
To give a correct idea of this animal, it must be drawn 
on a large scale, but my sketch (Fig. 1) will identify it. 
It would make a beautiful object for the microscope, 
as the skin is so thin that all the viscera can be seen 
through,’ 
When the larva is full fed, it crawls out of the water, 
and secretes itself amongst loose stones, in paling, or 
crevices of woodwork, &c. ; having fixed itself, it gra- 
dually contracts as the skin dries, and hardens until it 
assumes an oval shape (fig. 2) ; it is then of a dirty 
ochreous brown colour, the anterior extremity isa little 
depressed, having two horns above, covered with glands 
on the upper surface for breathing, and beneath them 
are two similar but very minute horns ; on the under- 
side are seven pairs of spots formed of black horny 
points, and a slight indentation shows the position of 
the mouth ; the tail although useless in this stage does 
not fall off. 
In the last week of August I discovered two pups 
amongst the Grass near the tub, and one of them pro- 
duced a female E. tenax the first week in September ; 
but there are still Jarvee in the tub and mostly full 
grown. In the garden are multitudes vf the Eristalis ; 
yet I never have been able to detect one laying its eggs. 
When the period arrives for hatching the fly, by dilat- 
ing itself, the depressed portion of the pupa, to which 
the four horns are attached, is forced off, and the fly 
comes forth of a pale colour, with its wings shrivelled ; 
it then ascends some object, when the fluids soon in- 
crease the wings to their proper dimensions, and the 
atmosphere hardens and colours the skin. 
Eristalis tenax is a Linnzean species of Musca. It is 
of a brown colour, the head is semi-orbicular, the face 
pale ochreous, pubescent and forming a short beak, 
which receives the troplie and lip; there is a shining 
brown oval space down the centre, with a darker spot 
at the top, beneath which are placed the antennze, 
which are small and drooping ; the two basal joints are 
subferruginous ; third dull black, compressed, or- 
bicular and larger ; on the back of this is in- 
serted a ferruginous pubescent seta ; the eyes 
are brown or copper coloured, large, very pubescent, 
contiguous in the male ; the three ocelli form a triangle 
at the base of the head; the thorax is orbicular-quad- 
rate, blackish with a brassy tint, the pubescence 
ochreous ; scutel transverse, semi-oval, ochreous ; ab- 
domen shining, tapering most in the male and some- 
what conical but truncated ; basal joint with a large 
semi-transparent ochreous spot on each side, and a 
transverse band of the same colour at the union of the 
segments ; upon the second is a smaller spot or line, 
varying in size, and the edge of this segment is ochreous; 
the abdomen in the female is more ovate, with the late- 
ral spots on the first segment, and the edge alone 
ochreous ; the wings are divaricating in repose, trans- 
parent, with an ochreous brown spot on the dise, very 
faint in the male; the submarginal cell closed before 
reaching the costa, one of the central cells looped, the 
nervures ochreous.brown ; halteres concealed ; legs 
six; hinder the largest ; tips of thighs and base of four 
anterior tibiæ pale fulvous, hinder broad, curved, cili- 
ated with ochreous hairs externally, with black inter- 
nally; tarsi flat, 5-jointed, basal joint the longest, fourth 
somewhat bilobed in the anterior ; pulvilli and claws 
ochreous, the latter pitchy at the apex ; Fig. 3. 
These flies are perfectly harmless, and do no mischief 
in the garden.—Ruricola. 
AUTUMN PLANTING POTATOES. 
Tug eligibility of planting Potatoes before winter has 
been much discussed. A fear was entertained that a crop 
so planted would be lost from the effects of frost. This fear 
was most certainly not founded, in Ireland at least, on ob- 
servation, for the least observant must have seen how 
few of the Potatoes left in the ground through the 
winter were injured by frost. The question has now 
been decided by a number of experiments, mauy of 
which are recorded in the Chronicle, and it is even 
affirmed by many that the Potatoes so’ planted 
have appeared to escape the disease more than those 
planted in spring. 
t was formerly the opinion of many, and I believe of 
Dr. Lindley himself, that diseased seed would produce 
diseased tubers ; experience has, however, now shown. 
several instances in which this has not been the ease. 
lalways had some doubts of it, and have previously 
given my reasons for questioning this ini th 
experience of several years in transplanting Potato 
plants, of which the sets had completely rotted off, from 
a disease that bore every token of being of the family 
of the one which now affects the Potato. We may 
therefore venture, with every prospect of success, to 
plant diseased Potatoes. 
The Dublin market is supplied with Potatoes (the 
Cumberland Kidney) from the county of Wicklow, in 
the month of May. They are planted on a strip of bog 
land, near the sea shore, in September, highly manured 
and set up in ridges with a heavy covering. When 
above ground, in frosty weather, two men with a hay 
rope pass along the furrows, and sweep off the hoar 
frost before the sun rises. It is a known fact, o? which 
most of your readers must be cognizant, that it is the 
breaking up of the cellular tissue in animals and 
vegetables by the sudden application of heat to a frozen 
surface that causes the destruction of the frozen part. 
By striking off the hoar frost from the leaves, this 
injury is in a great measure prevented. Upon the 
same principle, Potatoes planted on a western exposure 
willbe more likely to escape the effects of frost than 
those planted on an eastern one. I have seen this 
exemplified. And for the same reason, Potatoes 
planted among early spring Greens, where they will be 
shaded from the direct rays of the sun, will also be 
likely to escape. 
ineteen years ago I planted at Michaelmas, among 
Cabbages for winter use, some whole Potatoes, of a kind 
called ‘in Cork, Quarries. They sent up shoots early, 
many of which were destroyed to the ground by frost 
(and recollect it is only to the ground they are destroyed ; 
they may therefore at first coming above ground be 
protected by a covering of clay); but in a few days 
after, fresh shoots would appear, and at length they 
beat the frost out of the field, and I dug well grown 
Potatoes in May. Five or six years ago I dug Potatoes 
of a good size on the 15th of June from a planting of 
sets in January of Potatoes that had sent out strong 
shoots in the pits, leaving the shoots on them. It is to 
be observed, that the kinds planted were not the 
earliest, but the third or fourth earliest of the gar- 
deners, large field Potatoes. 
From the Potatoes having ceased growing so early 
this year, and from the warmth of the present season, 
those now digging out, whether diseased or sound, show 
either strong buds, in some cases shoots, or a disposition 
to shoot, and I have not the least doubt that the com- 
mon earlier kinds of Potatoes, if now planted, would 
yield us a sure crop in May or early in June; and as 
the premature ripening of the later kinds will probably 
give them a precocious property of production, and as 
the Cup (Minion in Cork) appears naturally disposed to 
early and quick production, I think we might also ven- 
iure to plant this valuable Potato (it is one of the 
firmest we have, and a strong proof of its value lies in 
its being known and grown all over Ireland) in the ex- 
pectation that it would acquire a reasonable growth 
before the appearance of the disease next summer. And 
as the Potato appears to suffer less from the disease in 
the ground than in the pit, we have in this an additional 
reason not to defer our planting till the spring. 
In Ireland an objection may be raised to autumnal 
planting in the want of manure, but straw alone has in 
many a poor man’s necessity been found to give him a 
good crop of Potatoes. They might in addition receive 
a top dressing in spring. I need not say what a sca- 
sonable relief it will be to have a general supply of 
new Potatoes by June next. 
As the diseased Potatoes send out strong shoots, and 
even earlier than sound ones, and as they havo been 
found to yield sound tubers, it would be advisable to 
plant the diseased Potatoes as well as the sound ones ; 
as they are of little value their loss would not be felt, 
and should they perish in the ground they would have 
done so in time for a spring erop.—J. M. Goodif/ 
Granard, Sept. 26. 
EXOTIC FERNS. 
Tue annexed list contains a selection of pretty kinds 
that any person may grow to perfection in a greenhouse 
or conservatory (either grouped by themselves, or 
placed amongst the other plants—whether exposed to 
the sun, or in the shade), where they will require no 
other care than what is bestowed upon the other plants 
in the house, of watering, shifting into larger pots when 
necessary, and occasional surfacin g when necessary. 
A mixture of two-thirds of loam, and one-third of 
peat, is suitable for potting all of them, except the 
Adiantums, which do better in peatalone. As many of 
the species grow to a considerable size, and require 
ots of a size to allow their free growth, the soil for 
potting them ought to be mixed with coarse drainers, 
to keep it open and porous ; and in potting at all times, 
drainers ought to be used in the bottoms of the pots. 
"There are many other species of Ferns that vill do 
better in.a greenhouse than in the stove ; but, as they 
