« ForrigeFortsett »
NEW DIVING APPARATUS.
185 The glass globe ought to be made with plan depends. If a diver or any person a very short thick neck, ipstead of a who has occasion to be under the surface curl, as they generally are, for the bet- of the water for a considerable time, ter fitting of the cork.
could, while there, breathe air of about I am, Sir,
the same density as on the surface, and
if any means can be devised to keep it Your obedient servant,
sufficiently pure for respiration, he might W--
remain under water as long as these effects could be continued.
The following description of an appa. ratus which would contain a supply of
air, and keep it in a state of purity, will NEW DIVING APPARATUS. not, I think, be wholly uninteresting to
I am, Sir,
N. B.-Upon an average, every time a man breathes he consumes about forty cubic inches of air; this is 800 inches per minute, allowing him to inspire every three seconds, and 48,000 inches in an hour. One and a half cubic foot of air, which contain 2592 inches, would be enclosed in a vessel of about seventeen inches diameter, and, condensed twenty times, would be more than 50,000 inches; so that a man might breathe for an hour, and then the equilibrium would scarcely be restored. The size of the apertures would be exactly ascertained upon the same principle as the Argand burners for gas.
Description, BALIMO A is a head-piece of strong copper, made in a globular shape, and sufficiently large to admit the head and neck to more without inconvenience,
BB, two strong glass lenses, to enable
the divers to ascertain the forms and Soos b9012
situations of objects. With he neben
C is that part of the head-piece which The und tons
forms the collar for the neck. du Y'19 h
D is a leathern dress to be attached to
the collar, C, to fasten tight over the yd 546h. ouirohlozb
breast and back, with sleeves for the budeme
arms, fastened tightly at the wrists, which birist od 1973
will prevent any water from being admitted, and preserve the divers from
any injuries by coming in coytact with Sir,-It having frequevtly occurred to
the rocks, &c. This dress should be me that an apparatus, upon an economięal and simple plan, niight be invented
covered with a varuish, to prevent it from
absorbing moisture.w to enable persons to descend to certain
sit depths under water, instead of the ex- E is a strong globe of copper, which pensive method of the diving-bell, I take the diver may fasten to any part of his the liberty of handing you a short de- dress which is most couvenient for him, scription of a plan for the purpose, and and attached to the stop-cock, E, by shall be much obliged by its insertion in means of a screw and a flexible tube. your widely-extended públication.
In this globe are condensed, by a forcing. The condensation of air into a smaller pump, 10, 15, or 20 atmospheres of space than it naturally occupies, is ef. common air. This, being a separate fected by the most simple means, and part, may be taken off at pleasure, and might be easily made applicable to many globes of different sizes substituted, acmore purposes than it is at present, and cording to the length of time a person it is upon this principle that the present has to remain under water.
EXPANSIVE POWER OF FREEZING WATER. Fis a stop-cock, terminating in a head, causeway are older than any man now which contains a number of very small living, and the space between them and holes, covered with a valve.
the lake is very narrow, scarcely extendWhen used, nothing more is necessary
ing 15 feet from the trees. Du than to fit the head-piece, A, with its
“The top of the rock is low at least collar, C, and the dress, D; charge the
two feet above the water. This height globe, E, and screw it on the stop-cock,
it is declared to have gained imperceptiE, in the lower part of the head-piece;
bly, year by year, for many years, in turn the stop-cocks, E and F, and all is
consequence of its advancing towards ready, when any person may, without
the shore, and -standing continually in danger, plunge into the water : he can
water more and more shallow. The lower himself, by means of weights, to
water is evidently of the same depth now any depth, and raise himself up again by
as formerly, as is proved by the appeara rope to the boat above; while the con
ance of the shore. stant stream of fresh air from the small “ When we came up to the rock, which aperture of the cock, E, will enable him was standing where the water was scarcely to breathe freely, while the foul air is knee-deep, we found a channel bebind continually forced out at the stop-cock, it, towards the deeper water, forined in F, and his atmosphere is preserved pure the earth, about fifteen rods in length; and respirable. When he perceives the it was serpentine iu its form, and was current of air from the cock, E, to sunk from two to three feet below the become weaker, he would conclude that common level of the bottom on its borit had nearly restored its equilibrium, ders. In the front of the rock, the earth and ought to ascend, while the water is was pushed up in a heap, so as to rise prevented from entering by the valve above the water, declining, lowever, at closing over the apertures at F.
the distance of a few inches, obliquely and pretty rapidly. Not far from this rock, we saw another much less, attended by the same phenoniena, except
that they were diminished in proportion EXPANSIVE POWER OF FREEZING
to its size. The whole appearance of .: WATER.
each was just as one would expect to
find, if both had actually removed from In Dr. Dwight's Travels in Ame
their original places towards the shore, rica there is the following passage : throughout the length of their respective
« Friday morning. October leth (says channels. How these channels were he), we rode to the south end of the lake, formed, or by, what cause the earth was accompanied by Mr. Whittlesey, to exa- heaped up in front of these rocks, I leare mine à rock, of which a singular, not to to the divination of others. The facts I say an incredible, opinion prevails in the have stated, as I believe, exactly." viciuity. Our road, for near half a mile, Dr. Dwight continues : lay on a natural causeway, about thirty feet in breadth, which separated the lake . "Several years since this account was into two parts, and was formed of earth, first written, I met with the following probably washed up by its waves. The paragraph in the collections of the Masrock which was the particular object of sachusetts Historical Society, vol. III. our curiosity, is said, by the inhabitants p. 240 :- There is a curiosity to be seen long settled here, to have moved a con- iu the Long Pond in Bridgton. On the siderable distance from the spot where easterly side of the pond, about midway, it anciently stood towards the south- is a cove, which extends about one hunwestern shore. You will not suppose we dredt rods farther east than the general considered this story as founded either course of the shore-the bottom and the in truth or good sense. However, having water so shoal, that a man may wade long believed it to be prudent, and fiftv rods into the pond. On the bottom made it a regular practice, whenever it of this cove are stones of various sizes, was convenient, to examine the founda- which, it is evident from visible circumtion of reports credited by sober men, I stances, have an annual motion towards determined to investigate this, as I saw the shore. The proof of this is, the that it was firmly believed by several dis- mark or tracks left behind them, and creet persous. Une particularly, a man the bodies of clay driven up before them. of unguestioned reputation, and long le- Some of these are perhaps two or tlirée sident near t
, that 40 tons weight, and have left a track seveyears since, the top of this rock, at the ral rods behind them, haying at least a ordinary height of the water, was at common cart-load of clay before them. least two feet below its surface, and 15 These stones are many of them.covered or 20 rods farther from the causeway with water at all seasons of the year. than when we saw it. The shore has The shore of this cove is lined with these unquestionably remained as it then was; stones three feet deep, which, it would for the trees and stumps standing on the seem, have crawled out of the water.
EXPANSIVE POWER OF FREEZING WATER, This may afford matter of speculation to ice forms firmly about the rock, and as the natural philosopher.'
it expands from the middle of the pond "Untit 1 saw this paragraph, I did towards the shore, carries the rock along not imagine that a story, such as I re- with it. The fact, that the ice does exceived at Salisbury, would ever be re- pand from the middle towards the borpeated." Vol. in. p. 245.
ders, in all cases where water is frozen, "Upon the preceding statement the
must be evident to all acquainted with
cold climates, and who have observed Quarterly Review remarks :
the circumstances in which ice is formed. "" Dr. Dwight has not stated the size
When water is left to be frozen in a vesof the rock which is said to possess this
sel, the expansion from the iniddle to extraordinary power of locomotion; if
the outside is so strong as to break the he had, it is possible that a story which,
vessel. This is sometimes the case even in another of his journals, he relates of
where the vessel is of iron. There is the Oneidas, might explain the apparent
often, also, a considerable elevation in prodigy. · Those Indians regard a large
the middle of the ice, resulting from the stone with religious reverence, and speak
resistance of the sides of the vessel to of it as their god, because it has followed
the outward expansion ; but in ponds them in their various removals, slowly
and lakes this central elevation is never indeed, but to a considerable distance.
formed, on account of the immense The truth is, a stout young man resolved
weight of the ice, * and the little or no to amuse himself with the credulity of his tribespren, and therefore, whenever he passed that way, took up the stone,
** The expansion of ice, though so which was too large to be removed by a great a force, that no known resistance man of ordinary strength, and carried it can confine it, is always exerted in the some distance westward. In this man direction where there is least resistance. ner, the stone, advancing by little and lit- I several times repeated the following tle, made in a few years a consi
ew years a considerable experiment before my classes, while progress, and was verily believed to have Professor of Mathematics at the Univermored this distance spontaneously. The sity in Rhode Island. I procured a miliyoung fellow told the story to an Ame- tary shell, weighing 70 or 80 pounds, rican gentleman, and laughed heartily and capable of containing nearly two at the credulity of his countrymen.. But quarts of water. The orifice was about had the rock which Dr. Dwight saw heen au inch in diameter. At the approach of of dimensions which would render a a very cold night, I filled it with water, trick like this possible, he would surely and placed it in a situation favourable liave suspected it; it is highly improba- for freezing. In the morning, all the ble that the samé strange and trouble water was frozen, and a column of ice some deception shoulıl be atteinpted in was driven through the orifice, of the two places; and in the statement quoted diameter of the orifice, rough in appearfrom the Massachusetts Transactions, ance, and five or six inches long. When some of the stones are said to be of two water freezes in a vessel of some strength, or three tons weight. That statement at first the resistance of the sides causes appears to have been reprinted from a the elevation of the ice adverted to above. Portland vewspaper, the place where the As, however, the icecontinues to thicken, phenomenou is said to exist being only and to oppose a resistance continually eighteen miles from Portland. Any increasing to the expansion upwards, a thing, therefore, which might be so time arrives at length, when the sides of easily contradicted or disproved, would the vessel present a less resistance to hardly have been published, unless it the expansion, than the super-imposed had been commonly believed. But if ice, and at this point the vessel is broken. science and literature are making such But when ice forms upou a lake, this progress in this part of the United States elevation cannot take place, on account as some suppose, the matter will doubt- of the very grent weight of the whole less be investigated as it deserves, and mass of ice, which weight, in ordinary the truth or falsehood ascertained of circumstances, prevents the expausion statements apparently so impossible.” upwards. Its expansion below into the
general mass of the water is hindered by The Rev. J. Adams, a correspond the water being contined on all sides, ent in Professor Silliman's Journal, and thus opposing a resistance scarcely gives the following explanation of
less than that of a solid body. The ex· those phenomena :
pansion, therefore, will naturally be di.
rected towards the shore, and a disrup156 The cause to which I am inclined to tion between the main body of the ice attribute them, and which appears 10 and the shore will be made, where the me satisfactory, is, the operation of the shore is inclined at a moderate angle to ice. The manner in which the effect is the surface of the water, and a projecproduced, I conceive to be this :--The tion of the ice will take place. This pro
188 RULES FOR CALCULATING THE LENGTHS OF PENDULUMS.
“ It appears also by the testimony, the shore, and must have been left in
that the principal rock now moves much that situation at the melting of the ice.
more rapidly than many years since, and When the ice formed again, it would be
this is what might have been expected, carried further forward, and since in
according to the explanation I have sugNew England the ice forms and melts
gested. When the top was 'two feet at often several times in succession during
least' below the surface, only the thickest a single winter, it is easy to see that in
formations would reach it, and of course several years a rock might make very
its progress would be very slow. When perceptible progress. I have also no
the top reached the surface, the thin ticed, that, in New England, fences formations would effect it, and when it whicli originally stood erect, hear the rose above the surface, it would be edge of the grounds, covered by water
grasped in the middle by every successive during the winter, have considerably formation and would be carried forward inclined towards the shore as soon as
by the whole amount of the expansion. the ice was formed, aud fences in this « The circumstances of the channels situation always require to be placed behind the rocks, and the earth heaped upright in the spring. It is well known
up before them, render two things eviamong the farmers of New England,
dent:- First, that each rock was always that, if a stone fence is erected in a si
moved in a position similar to itself, milar situation, it will, after some time, be overturned. These instances show
without ever being turned over ; for if
the motion had been produced by reboth the reality and great force of ex- peatedly overturning the rocks, they panding ice. It is no objection to this would not have left channels behind explanation, that the principal rock them. And cain an immense forre which Dr. Dwight saw, was originally, must have been exerted to remove these
rocks, especially when we consider that
one of them weighed, by estimation, 40 jection must have often been seen, by
or 50 tons, and when we add to the re. every one accustomed to cold climates,
climates, sistance arising from its weight, that when thick ice is melting, as it fre
which must have been caused by the quently lies several feet beyond the edge formation of a deep channel after it, of the water; and if the fracture of this The expansive power of ice is a force ice be examined, the appearance indi- abundantly sufficient." cates that the lower part of the formation has been forced outwards.
“Whenever the shore is perpendicular to the water, or approaching to it, this projection cannot take place in any consi
PRACTICAL RULES FOR CALCUderable degree, and in such circum LATING THE LENGTHS OF PENstances I have seen the ice cracked in DULUMS. many places, and numerous planes joined
Sir, If you think the following at the crack, elevated so as to be gently inclined to each other, like a very flat
practical rules for calculating the roof. This was the natural effect on the
lengths of pendulums, &c. would be mechanical principles which must govern useful to any of your readers, I shall the results. My views on this part of the be obliged by your giving them a place subject are very much confirmed by the in your very valuable Magazine. circunstances of the Deerfield disrup
Ist. To find the length of a pendu. tion.' In this instance, the earth, to the
lum that shall make any number of depth it had frozen the past winter, 14 inches, was broken in a straight line above
vibrations in a given time, as one six rods, and the south edge of the fissure
minute. having been forced up, overlapped the Now, it is demonstrated by writers other three feet.'”
on mechanics, that n?: 602 :: 39.14:L;
RULES POR OALCULATING THR LENGTHS OF PENDULUMS. 189 therefore, by multiplying means and of gravity in the time of one vibraextremes, and dividing by ne, we have tion of a pendulum, is to half the 602 x 39.14
length of a pendulum as the square L=
, whence n= the num. of a circumference of a circle is ber of vibrations made by a pendulum to the square of its diameter, that is 39.14 inches in length in the latitude (denoting the space fallen through in of London, and L equals the length. a second at the given place by S, and
the length of the pendulum by L). EXAMPLE 1.
S: L:: 3.141592 : 1; therefore S =
LX3.141592. What is the length of a pendulum that makes thirty-five vibrations in
EXAMPLE III. one minute?
Through what space would a heavy Now the above expression becomes body fall from each in one second of - 60% x 39.14 115inches, the length
time, when a second penduluin is 39.14
inches in length ? required.
Now L=39.14, therefore S=19.57 x 2nd. Having the length of a pendu
3.141594 =193.14 inches. lum given, to find how many vibrations By the converse of this method we it will make in a minute.
can find the length of a second penduFrom the above expression, viz. L=
lum, having the space fallen through
hy a heavy body from rest in the first 602 x 39.14
second of time.
Take S = * 3.141592, and multiEXAMPLE i1.
plying each side of the equation by 2, How many vibrations will a pendu. we have 2 S = L x 3.14159o ; therefore lum, 115 inches in length, make in L- 28_ one minute ?
L = 3.141599 Now the above expression becomes
EXAMPLE IV. 602 x 39.14 eV 115
What is the length of a second pen35, number
dulum in the place where a heavy body of vibrations required.
falls, from quiescence, 193.14 inches in 3rd. Having the length of a pendu
the first second of time? lum vibrating seconds in any place Now S = 193.14 inches; therefore giren, to find the space through which
1-2 193.14 a body falls in a second by the force of * 3.141598
w = 39.14 inches, the gravity.
length. Now it is demonstrated by mathe- All the above examples are very maticians, that the space through readily solved by the sliding rule, as which a heavy body falls by the force follows.
6 02 39.14
, we findns
which, in words, is this :-Set the pendulum on C; or set the length of number of vibrations given on the line the pendulum given on C to 60 on D, marked D to 39.14 on C, and against and opposite to 39.14 on C you have tbe. 60 on D you have the length of the number of vibrations per minute ou D.
EXAMPLE . C | 19.57 ... 193.14 inches, space fallen through in one second. DI . 14159,