The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1836-12-16 00:00:00

THE LIVERPOOL STANDARD.

LECTUREI,III.

On Saturday evening Mr._Hemming continued.
Water exists naturally in three separate states. e It exists in
the solid at the arctic and antarctic regions, in the liquid be-
tween the temperatures of 32 .and '212, and in• the vaporous at
all temperatures. - It is erroneously supposed that Water will not
vaporize under '212 degrees: ice itself wilt •do so. Steam is the
vapour of water at 212 degrees; but vapour is the term applied
when vaporization takes place at lower temperatures. r here
•
are various causes which regulate vaporization, amongst these
temperature, the motion of the air, and its..dryness, are the
principal. The amount.of evaporation, as stated.•ut,the: preced-
mg lecture, which takes place daily, is so prodigieue that had
we not sufficient data for the fact, it would appear incredible.
We find the quantity of vapour held in solution by the .atatos..
s_phere to be variable; under •stime •circumstances, as when the
Harmattan blows, it is almost dry. Ureter high temperatures
there is a targerquentify of vapour contaitied.in the atinenphere,
and this often when we . think it is th'eT, rpst.., -iplls, on
, hot day, t here 'f's a eery eeriseat - quept ityl, gelpriF,lll:4_4ll4.
in it.... 4. very l'aAigitlh&raitY 'Of Vapoterli' ' reeepiljoniithit, e'
• ferne of affil, rain, and snow; but a-veryefeesatequeentete'ita eif-peigia.
returned is tin rAiifft'isti Oleifoeti4 nr dAi.:;;llir•,,*vMemor,itt
lof
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1 11. e. ;TIT .rii of the increasB i?'6'5.d1,16;,..*, t,ut
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4:00.,,pe4e 11146 &Bt.!, Me initYkiii
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~7s!..oi:lole''-41;; . , OnObe p i udi(4o4 44,9:8140$
tivaplOratiu4 iit'll tkilileNt ti*Valitiriae. tile. day,' au ,14:1 t
eslol4:fiko4treifiaziV at :falling i 4 a inist,or dew .up eti Citt!eenre..
'cue ,(iftlia eartli,, Or.liii.ton iinaicines that -wllen tWO, clouds.
,;r4iffe're.iit tenipereteres'4leet, there is en interehenge of edit,-
ric ; and:as:the ureen temperature thereby produced 'ail'. not
holtl the .saneeceeatitity of yapour in solution, thate he siipeilloity
is precipitated in the form of rain, snow, or hail.. The. other
theory lathe eiectricetheery, in which it is Mentioned that the:
aqueous particles of the clouds exist in different states of clete ;
tacit y with eegard to each other, and that when a elouil posi-
tively charged with electricity approaches one negatively charged
an iiitereleange of electritity will take place, and rain be pre-
cipitated. We find that electricity does tend to precipitate j
waterefor, ifs 'sponge be soaked in water, and well Squeezed, we
~can cause it to give out more water by the application of elec-
tiicity. , In the sane manner, if we take a sypiani of such a mi-
nute diainater that the water will only issue front it drop by drop,
and connect it with an electrical machine, the water will'ilow in
a eoutinuous stream. Each of these theories tnay be correct—,
there is nothing to militate against either of them. We have
only-lately been acquainted with the theory of dew, and we are
indebted for it to Dr. Wells. It was known that dew was only
precipitated when it was most wanted—on a cloudless night,
when the plant seems must to require it; but no correct notions
were eutertained with respect to the cause of this phenomena.
Dr. Wells found that the earth is warmerat night on the surface
than a few 'feet above it. This is accounted for by the earth
giving back again at night the beat which it received from the
sun during•the day. This heat, if there be no clouds to inter-
cept it,' will pass off into space. On this account it is found that
if a thermometer is placed on the ground ou a cloudless night it
may staud in our climate from 10 to 15 degrees higher than .it
will at six feet from the ground. The consequence of this is,
that the vapour contained in the atmosphere on the surface of
the earth will be precipitated upon its arrival amongst a colder
Stratum of air, and fail down in the form of dew. Dr. Wells
was led to this by several experiments; for example, he placed
small portions of cotton wool upon sticks, at certain altitudes.
If the night was cloudless the wool was found to have increased -I
in weight; but in every case, if he covered the wool with a pent
house or a handkerchief, there was little or no dew. precipitated...
This is the reason why We have no preciiitation on cloudy_
nights, because the heat that is given off by the earth is:
received by the clouds, cad returned back again, by whieh the
deposition of dew is prevented. Dr. Wells candidly aCknow-
ledged that in the pride of his heart he had laughed at persons
who covered their plants at night, little supptisieg that by..this
means the radiation of the heat of the earth around the plants
was prevented, .. .. • ' • •
We have now to consider the boiling points of water. under
diffeient circumstances. It is found that whatever degree of
heat we apply to water, that is, whenever it is eepaiied to the
atmosphere, we cannot compel it to assume a higher tempera
ture then 212 degrees. At that heat it begins to boil. This is
our usual exposition of the boiling point et water; but it is an
incorrect one, for at the bottom of some. of the London brewers'
boilers, in which the liquor• is 30 feet high, the temperature is
250 degrees iii consequenee of the pressure of the column of
water, which is equal tneptither atmosphere. It is 4 fact. that
none but the great breWhimses of ' Loudon eon brew porter of
much better quality. thanthe smaller ones. The probability is,
that this superiority is owing to the depth of their boilers, as.
by that means they may he able to extract a certain quantity of
matter which cannot be extracted at lower temperatures. It
we boil water in VaCtlo, we shall find that the teniperature of
the boiling water will be only 88 degrees instead of 212; and we
find that, its we ascend e. mountain, the water boils at a lower
temperature as the atmosphere becomes rarer. Saussure
boiled water. at the top of Mont Blanc at 187 degrees. ,Dr.
Wollaston constructed an instrument on this principle for meet-.
suring, elevations, by indicating the temperature of boiling water,
on which a degree was divided into a thousand parts. We find
that, if water boils at 212 degrees on the surface of the earth, it
will boil at one degree lese:sso feet high. 'Dr. Wollaston found,.
by means of this instrument, that there was an .appreciable dif-
ference hetvreen water boiling an the floor anti water boiling in
.the same vessel on a table, The variation of temperature was
very visible between the water boiled in the cellar of a house
and in the garret. - Tito heieht of St. Paul's Cathedral wee_ cc-
.-t,ee.........ieee uy this instrume... 0.... az e iiiii tiug env:
ascended in a balloon for'the purpose of contrasting the indica-
tions of altitude furnished by that instrument with those of a
barometer. He kept the water boiling all the time he was in
the air by means of sulphuric acid and water. On his return,
he gave the iudications of' the barometer to a friend of his to
calculate the different elevations, whilst he himself calculated
those of Dr. Wollaston's instrument. When they met to com-
pare their calculations, there was only 11 difference of six feet
between them. although the hellion had ascended two miles in
height. This will show that we may measure altitude with as
much precision by Means of a boiling liquid as by means of a
column of mercury. We say that water boils at 212; but in
reality it seldom boils at that temperature. Much depends upon
the state of the atmosphere, the vessel in which the water is
boiled, and the purity of the water, and from these causes there
in a difference of several degrees in the boiling point. The heet
which is imparted to water after it has reached the boiling point
is carried off by the steam in a latent barn; end it has been
calculated that it requires 1000 degrees of heat to convert water
intri steam : 'This latent'heat becomes free again as the stearri
is con vei:ted intO water. If •this quantitseOf heat were not car.
ried eway With the vapour, the inevitable consequence would be,
that the inefant . water raiiched7the Boiling, temperature,. the.
.whale mass would be carried awayeimultaneottsly:, and produce.;
'it terrible' explosion.. Ice also absorbs latlat:heiit in its con
version into water to the amount of 140 degrees. The simplest. .
Mode of proving this is to mix a pound weight of -water at 32 .
degrees with another pound in 172 degrees, when the water will`
`be found of it mean teuipsirtiture; but if a peund weight of water
at 17'2 be mixed with a pound or pounded iceethe Ampere t tere
will be reduced to 32 degrees. We are indebted tai Dr. Meek,
ferohr'knowledge of this property of ice. lie ',
' "" led 10 e111(4-'"
,rein the idea that'such wasa be case by noticing thaf'-thefitirt,iice
of his eend 'was crieered..with ice although the temperature of .
the itir,itad bei.n. at 40 digtees for several days previettsly. 'He %.
immersed- a ,tbereviineter.in • the pond, anti ttiund. tb.at, it re-.
mauled .Stationary at 32 degreet until the whole of, the ice..cone
tained iii the pond wee dis Solved. In the sonic inanner, when •
water is
,cenverted into iceeit gives out a portion of,:heit, and..
expapde.l-10th (if its bulk. Mr. Herriming illustrated tins by
freezing unite water in a bottle, when it cracked in every direc-
tion. According to some experiments made by the 'Fiorentine
academicians., it was found that this expansion takes place ,with
a force of.27ltonsein tha square inch. The disitife'-rrati" of
rocks is owing to this circumstance. The rain which has en-
tered their pores in the autumn freezes, and the e.xpatisitei which
takes place' tears the strongest rocks asunder. Rapid evapora-
tion, by taking away the caloric from the water, produces ice.
Mr. Hemming beautifully illustrated this by means ,of Dr.
Wollaston's oryophorits, tfie principle of which he explejned:
When water is heated in a boiler, the fire should always be
applied to the lower surface, as water is with elifficulty heated.
from above. Mr. Heminiug illustrated this by
means of a glass
tube containing water, at the bottom and top of .which were
pieces of lard. He applied heat to the middle of the tube, when
the upper portion of lard melted, and the Water boiled, but the
lard at the bottoM of the water remained in the• eolid state.
This arisCs from the .bad conducting ',ewers of water. This
may likewise be illustrated by colouring some water and heat-
ing it. when it will be found that the heated water may be
poured upon cold water without mixing with it. The densities
of fresh' and sea water are very different ; ' hence persons sWini
with more ease in the latter than in the former. The water Of
the Dead Sea is so remarkably buoyant that a person may fleet
in it with his head and shoulders out of the water without any
exertion, :This difference of density is owing to the satiric
matter which sea water contains in solution. Air. Hemming
'ills gritte(' this by caieiing alaittle-te rise front the bottom of a
glass jar '.by .adding salt to the atltter. • -