1846. THE CULTIVATOR. 141 
stantly giving out heat, but the temperature does not 
lower till it is all frozen, as it is the latent heat only 
that is passing off. 
Application .—The applications of these principles 
are very numerous and important, some of which, here 
mentioned, may not strictly appertain to the kitchen. 
1. Metals being good conductors, they are best for 
vessels over the fire, the heat passing readily through, 
to the substances contained in them. Hence, too, why 
copper, which is one of the best conductors, is em¬ 
ployed as the healing-rod or tube, for lard lamps. 
Wood, being a poor conductor, is advanfageousty used 
as a handle for vessels and tools which become heated, 
by not burning the hand. Hence also, the reason that 
earthen-ware tubes are best for the insertion of stove 
pipes, through wooden partitions, when metals by con¬ 
ducting the heat rapidly to the wood, might set it on 
fire. 
2. Different substances and surfaces radiate heat very 
differently. Light and porous bodies usually throw it 
off from themselves, much more rapidly than heavy and 
compact ones; and smooth and polished surfaces more 
rapidly than rough surfaces. Hence the heat thrown 
off from a large fire of burning wood and charcoal,—■ 
porous substances—burns the face more than the heat 
from a metalie stove, not a porous substance. Polished 
metals radiate very slowly; hence water will remain 
hot much longer in a tea-pot, kept bright and polished 
by the neat housewife, than in the tarnished tea-pot of 
the careless one. For the same reason, pipes for carry¬ 
ing heat by hot water or hot air furnaces, should be 
bright, in order that none may he wasted on the way, 
till it reaches the place of destination. Hence also the 
reason why stove pipes and drums made of polished 
Russia iron, do not throw off so much heat as iron whose 
surface is rough, or rendered porous by blacking. 
Substances radiating freely, absorb also freely; and 
those radiating little, absorb little. Hence the reason 
that a polished tin plate, placed under a hot stove, or 
beside it against a wooden wall, remains cold, and pro¬ 
tects the wood. Hence also, as every cook knows, a 
bright baking tin will not absorb heat and burn the 
bread as a blackened one will; and indeed it often pre¬ 
vents the proper degree of baking, which is at once ob¬ 
viated by giving it a slight coating in the smoke of a 
lamp. A new tin boiler, over a clear and hot charcoal 
Are, failed to boil water at all; the reason being sus¬ 
pected, a few shavings of pine were thrown into smoke 
the surface,—when the water soon boiled rapidly. 
Hence the utility of the thin coating of soot which 
forms on the bottom of boilers. 
3. Boiling water, (in all ordinary eases,) being al¬ 
ways at 212 degrees Far., it is obvious that a pot of po¬ 
tatoes will cook just as fast when boiling slowly as 
when boiling very fast; hence the notion of cooking a 
boiled dinner faster by a very hot fire, is founded in er¬ 
ror, and only wastes fuel. The great amount of latent 
heat carried off by steam, renders it important to keep 
boiling vessels closed by metal covers, which condense 
steam, and return in part the latent heat. Covering 
newly baked bread, by a cloth, condenses the rising 
steam in the same way, and keeps the crust soft. It is 
the amount of heat required for evaporating water, 
though by the slow process at common temperatures, 
that occasions the cooling process of sprinkling rooms 
m hot weather. The more rapid evaporation of ether 
and alcohol, render cooling by these substances more ef¬ 
fectual and rapid. Baked potatoes remain long hot; 
but if the skin be broken, to let out the steam, they 
soon cool by the passing off of the latent heat of the 
steam. 
Were it not for the latent heat required to convert 
snow into water, warm weather would dissolve at once 
our snow-banks into liquid, and tremendous inundations 
would be the consequence. From a similar cause, the 
water in the dinner pot is not boiled off at a flash, and 
the dinner spoiled. 
Water freezes sooner than many other substances; 
hence often the. water freezes and leaves them when 
they are mixed or in solution. Hence the ice moun¬ 
tains of the polar seas are fresh; and hence the concen¬ 
tration of vinegar, lemon juice, and maple sap by 
freezing. 
THE YELLOWS. 
Mr. Tucker— The yellows in peach frees, is a sub¬ 
ject that still continues to be interesting in this part of 
the country. I wish, therefore, to communicate a fact 
which may be of some importance in our inquiries after 
the cause of that disease. 
Four years ago, Mr. B. Silliman, Jun., of this city, 
procured from Liverpool a considerable number of 
young peach and nectarine trees, budded on plum stocks. 
Some of them were put for standards and others walled 
upon a board fence. There had been no peach trees for 
twenty years on the ground where those were planted. 
They grew well the first season, and appeared in per- 
feet health. The second season some of the peach 
trees showed symptoms of yellows, and died the third 
season. At the present time, (February, 5 46,) no one 
of the trees, either nectarine or peach is free from 
disease. In the garden adjoining that of Mr. Silliman 
there were diseased trees standing at the time the im¬ 
ported trees were planted out. 
The following inferences may perhaps be safely 
made from this experiment. 
1. Budding on plum stocks, is not a security against 
the (( yellows.” 
2. The plum tree has not hitherto been known to be 
liable to the disease. We may therefore conclude that 
the disease commenced in Mr. Silliman's trees in the 
peach and not in the plum portion—that is, in the top, 
and not in the root . This furnishes a strong probability 
that it is the natural course of the disease to commence 
and be seated primarily, in the part of the tree above 
ground. 
3. The disease did not arise from anything inherent 
in the trees, but from some cause external to and discon¬ 
nected from them. The ground of this conclusion will 
not be apparent without taking in connection with what 
has been staged, the fact, that the “ yellows ” is un¬ 
known in England. This conclusion bears pretty di¬ 
rectly upon an important theory, which has been very 
ably presented to the public in a recent work, and met 
with a favorable reception. The theory is thus stated:—• 
The yellows is “ a constitutional taint, existing in 
many American varieties of the peach, and produced in 
the first place by bad cultivation, and the consequent 
exhaustion arising from successive over crops. After¬ 
wards it has been established and perpetuated by sow¬ 
ing the seeds of the enfeebled tree. 55 
It is most sincerely to be regretted that any fact 
should present itself, that seems irreconcilable with f a 
theory, which offers to us, if correct, so ready and sure 
a means of having healthy trees. According to the 
theory, trees procured from regions where the disease 
has not appeared—England, France, Italy, China, or 
even our own u Great West,” for example— should be 
free from disease, and should continue so, if planted in 
an unexhausted soil. Mr. Silliman’s experiment leads 
us to apprehend that we are not in that way to escape 
the evil. 
To see that we make no unwarranted conclusion, let 
us advert to the facts and circumstances involved in this 
trial of foreign trees. It is well known that the yel¬ 
lows ” has not appeared in England. Mr. Downing, 
( <e Fruits and Fruit Trees of America,” p. 467,) states 
a further fact, that “notwithstanding the great number' 
of. American varieties of peach trees that have been re¬ 
peatedly sent to England, and are now growing there, 
the disease has never extended itself there, or been com¬ 
municated to other trees.” Peach trees in England, 
therefore, have no constitutional taint, that makes 
them liable to .the l< yellows;” and if they remain there 
they never take the disease. But bring these trees to 
New Haven, and in fifteen months after their arrival 
they are dying with the “ yellows.” There must there¬ 
fore be something here which is not there. The disease 
shows itself too soon after the trees reach this country to 
admit of the supposition, that the exhausting process©*. 
