434 JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. [ November 10, 1881. 
The reading of works on gardening is very essential, and should 
be particularly attended to by every young gardener. As standard 
works we can recommend Thompson’s “Gardener’s Assistant” and 
Anderson’s “ Practical Gardener but we give preference to the 
reading of weekly gardening papers. My employers have paid 
for two papers every week now for nearly ten years for me, and I 
take out one on my own account. Of the three I may, perhaps, 
be allowed to say I give preference to the Journal of Horticulture 
either for young gardeners or old. The matter which it contains 
is instructive and reliable, and bears testimony to the abilities of 
its staff of contributors, composed as they are of the leading prac¬ 
tical gardeners of the day. Young gardeners should also attend 
to the study of history and geography ; and as they spend years of 
their youthful prime in bothies, exposed to many allurements, we 
wish to caution them against the reading of novels. No doubt 
there is the old adage that “ reading makes a learned man, and 
writing makes a correct man,” but in our opinion reading novels 
never added anything to any man’s learning. Many of them are 
so alluring that it requires great steadfastness to resist their tempta¬ 
tion. Much trashy reading corrupts the mind of the young, and 
is too often the promoter of alternate follies taking the sway, and 
when such is the case with young gardeners they will rue it. We 
have said, Neglect novel reading ; we say also, Neglect dominos, 
draughts, and card-playing, and, above all, neglect the beerhouse, 
and things will go well with you. In the first place you will be 
more respected by the gardener whom you are under, you will 
also be more respected by those who are above you in every 
station of life. The crown and glory of life is character. Smiles 
says it is the noblest possession of a man, constituting a rank in 
itself; it exercises a greater power than wealth, and secures all 
the honour without the jealousies of fame ; it carries with it an 
influence which always tells, for it is the result of proved honour, 
rectitude, and consistency—qualities which, perhaps more than 
any other, command the general respect of mankind.—H. Elliott. 
REVIEW OF BOOK. 
Handy Booli of Fruit Culture Under Glass. By David 
Thomson. Second Edition. William Blackwood & Sons, 
Edinburgh and London. 
Mr. D. Thomson’s excellent manual on fruit culture is so 
well known and so generally appreciated by practical gardeners, 
that lengthy reference to it is quite unnecessary. The fact that 
a second edition has been called for is a sufficient indication of 
its popularity. The various chapters upon the Pine Apple, Vine, 
Peach, Nectarine, Fig, Melon, Strawberry, and Cucumber have been 
revised and some minor additions have been made, but in general 
there have been few alterations, for few were needed. In addition 
to the carefully written and useful calendar of monthly operations 
requisite in fruit houses, the chapter upon heating by hot water 
which appeared in the first edition is repeated. This is of such 
a thoroughly useful character, and we have had so many inquiries 
on the subject lately, that we give the greater portion of it in the 
author’s words. 
OBSERVATIONS ON HEATING BY HOT WATER. 
“ Notwithstanding all the elaborate essays that have from time to 
time appeared in the horticultural press on heating hothouses with 
hot water, I have the best reasons for believing that many whom 
the matter intimately concerns have still but very vague and erro¬ 
neous ideas regarding the principles upon which the proper adjust¬ 
ment of hot-water boilers and pipes depend. 
“ It is my belief that, if those who have to do with fixing pipes and 
boilers were to make themselves acquainted with the effects of heat 
and the power of gravitation on water, it would be next to impossible 
to commit the blunders, and resort to the unnecessary and expensive 
precautionary measures, one so often meets with and has to deal with. 
It is no part of my intention to pretend to deal with that imponder¬ 
able and powerful agent called by men of science caloric, but which 
I shall call heat—hypothetically regarded as a subtle fluid, the par¬ 
ticles of which are to each other repellent, but attractive to all sub¬ 
stances, though in various degrees. But the effect of heat upon 
water, an element composed of minute and distinct particles that are 
supposed not to have the quality or power of transmitting heat the 
one to the other, as in the case of solid bodies, is one of the matters 
concerning which some knowledge is indispensable in the case of all 
who have anything to do with heating by means of heated water 
circulating in pipes. 
“ The particles of which water consists, it need scarcely be said, have 
a capacity for heat from different sources, but most manifestly so to 
us in this case from combustion in the fireplace. Now the expansion 
of bodies is one of the most universal effects of increasing their heat. 
This expansion takes place to a greater degree in some bodies than 
in others. Liquids expand much more by the same inci'ease of heat 
than solid bodies, and air more than either. With the expansion of 
the individual particles of water their specific gravity becomes less ; 
in other words, they become lighter in proportion to their size. Here 
lies the whole secret of hot-water circulation in pipes and boilers, 
and the well-known law which should regulate their relative posi¬ 
tions. The heated particles of water bound upwards, and, as ‘ Nature 
abhors a vacuum,’ their place is taken up by a rush of colder and 
heavier particles. It is of very little practical use to cavil about the 
question as to whether heat or the greater specific gravity of the cold 
water which jostles up the warmer and lighter plays the greater part 
in sending up and away the stream of hot water. Both have a hand 
in it no doubt. This influence of heat upon water can be very mani¬ 
festly shown by filling a tumbler with cold water, and mixing with 
it some coloured particles of matter, and then immersing the tumbler 
in a vessel filled with hot water. It will at once be seen, by the 
motion of the particles of coloured matter, that at the sides of the 
tumbler there is an upward current of heated and in the centre a 
downward current of colder water. This goes on until the whole is 
of the same temperature. A glass of warm water immersed in cold 
has the current reversed in its course—upwards in the centre, and 
downwards at the sides, where the water is being cooled. Here is 
the whole secret of the motion and course of heated water in the 
boiler and pipes of a properly adjusted heating apparatus. And one 
would suppose that the simple understanding of this would prevent 
any from making mistakes. Yet, strange to say, some who under¬ 
take hothouse-heating are entirely ignorant of these simple and well- 
established facts. 
“ Wherever the heat generated by combustion in the furnace acts 
most directly and powerfully, from that surface bound upwards the 
particles of water, and to that spot, simultaneously, drop the colder 
particles of water, to be in their turn sent bounding on their errand 
of warmth. Anything that attempts to contravene this law of 
gravitation will be rebelled against by the elements concerned with 
unmistakeable violence and persistency. Clearly, then, the outlet for 
the water, thus lightened and charged with its freight of heat, should 
be at the highest part of the boiler ; and that by which the cold 
water is to run in and down, to take its place, should be at the lowest 
point. Boiler inventors and manufacturers recognise this important 
part of the matter, and always place the flow pipe at the highest, and 
the return pipe at the lowest point of boilers. 
“ Great importance has been attached by many to the necessity, or 
at least the great desirability, of having the boiler fixed at a very 
much lower level than the pipes, and also to the necessity of laying 
all the flow pipes on the incline the whole length of the house to be 
heated. The importance, too, of having the return pipes on a con¬ 
siderable decline has, in my opinion, been very much over-estimated. 
It is entirely unnecessary to form deep damp stokeholes in order to 
sink the boiler to a level much below the main body of the pipes, as is 
so very frequently met with. And as to having the pipe3 running at 
an incline after starting from so high a level, I consider it entirely un¬ 
necessary. Indeed, one of the most efficient heating apparatus I ever 
superintended started from about a foot above the level of the boiler, 
and ran down a gradual decline into the boiler. Immediately the 
water enters a hothouse it begins to part with the heat absorbed 
from the fire, gets colder, increases in specific gravity as it speeds in 
its way back to the boiler again, and a downhill career is most natural 
to it as soon as it leaves the highest point of action, where its heat 
is the greatest. Practically I have never found much difference when 
the pipes went the whole length of the house on an incline or on a 
dead level all the way round till it came near to, and dropped into, 
the return-opening of the boiler. Indeed there is little fear of a good 
circulation provided the pipes do not at any point descend and rise 
suddenly, and most especially that at any point they do not dip 
below the level of the return-opening into the boiler. I have had 
the working of apparatus where pipes, descending perpendicularly, 
crossed under a walk and rose again perpendicularly to heat another 
range of 80 feet of glass; but at none of the points were the pipes 
lower than 2 feet above the level of the return-opening into the 
boiler. This undesirable arrangement worked pretty well until hard 
firing became necessary, then the water was thrown out in plunges 
at the supply cistern. Such an arrangement should always be 
avoided. 
“ There is another error frequently committed in arranging the 
route of the water. Suppose, for instance, a boiler fixed at one end 
of a house of, say, 80 or 100 feet long, as part of the work allotted to 
it. As in the case of span-roofed houses, it may be desirable to have 
three or four rows of pipes all round the house. Now it is not un¬ 
common to find two rows called the flow-pipes taken all round the 
house to near the boiler, and there to start back with other two on 
the same route into the return-opening of the boiler. This is giving 
the water a long journey, and the return-pipes will be found com¬ 
paratively cold by the time the water gets to the boiler. Now, if 
instead of this the whole four pipes be connected with the flow-pipe, 
and go round the front and end of the house nearly on a level, and 
start along the back down a decline to the boiler, and there plunge 
down the drop-pipe into the return-opening of the boiler, it will be 
found that while any portion of the pipes may not be quite so hot as 
the beginning of the two flow-pipes in the former case, there will not 
be any portion of them nearly so cold as the last portion of the 
return. I do not say that this is the best way to conduct the water ; 
but I have proved from experience that the arrangement indicated is 
the better of the two named, when the pipes are, from any necessary 
conditions, laid all round the house in this way. 
