The Wonder Island Boys: The Mysteries of the Caverns

d in that way it was useful in letting us know what the weather would be. Before we sail, would it not be well to make one of

because with the barometer and the compass we shall be e

nything to do with the weather. Is the air pres

ascends, d

an unders

. On the other hand, moist air is heavier than dry air. These two co

o tell it is going to rain. We know it and feel it. What I particularly wanted to kno

n. The instrument shows the present pressure of the atmosphere, and its variations correspond to atmospherical c

ned from the instrument when t

but if the fine weather has been of long duration, and the mercury may fall for two or three days before any percep

indicates d

adily and slowly, fine weather will come, though two or three wet days may first elapse; and the fine weather wi

ase at all tim

wind; in the summer or in hot weather it prognosticates a thunderstorm; in winter, after frost, a sudden fall of the me

be pretty well versed in the weat

ce with its use is absolutely necessary; it is not a very satisfying device for those w

e compass was brought out for the purpose of securing it in a lit

tools which would make fine and carefully pivoted balances, but eventually this was done,

he next thing in order. This occupied several days. Instead of taking the bedding in their house, it was

hich could be sealed up, to hold a reserve supply of water. In addition two other vessels were also provided for the reg

o prepare most of the food before starting; but George insisted that the sma

ion for?" was George's inquiry, as they

Professor ventured the opinion that at leas

ld lady who attended a special meeting of prayer for rain? She came with an umbrella, and the people laughed and chided her. The minister reproved them, saying: 'She, at least, has faith, which you ha

Professor believed they were really going to find their former

a double meaning, and it is not venturing too much to say that their feelings were most tense

ng who were the owners of the habitation, their present destination, and briefly relating the knowledge they possessed of the inhabitants of the

ailed to the mast, to replace the small tablet which had hitherto fill

g the past month. The storm was severe during the entire night, and abated somewhat in the forenoon, but it

unt of its widespread character. The sea for hundreds of miles has been subject

n doesn't mildly or easily brook waiting. They did not know what to do, or how t

took no heed of it. However, he encouraged them in every effort they mad

ng hours, George could not hold in any longer, but broke out impatiently:

d better venture a start

risk. Harry, too, was anxious and nervous,

to take any risks. If we knew something of the conditions on the island, and had a certain knowledge that our comrades were in danger, the considerations I have named should not deter us from starting. B

of these things, and I feel that the

s a reason why they should consider their actions in the matter. It was so unlike hi

romulgating his great thesis; some of the most marvelous inventions took years to bring out and develop into such a state as to make them acceptable to the world. Delays, patiently borne, make strong men. The impetuous think they represent

of Cataract, in a shining sun, bound for a haven which might mean rest, or to a shore which might offer no welcome to them. The wind was coming mildly from the north, and when they had cleared the shore line and were beyond the influence

o the west as far as they could see, and when night set in the faint mi

, and the boys were constantly venturing guesses as to the distance traveled. The

have gone during the da

traveled at the same speed during the entire course that we made duri

t is three mil

ured it by triangulation some time ago, using o

glected to take

ur object in

eed our boat could make. If we knew the speed of th

sailing due west. Would not the difference in the speed

uld have made that distance. The wind has been variable at different poin

nd been during the day; I

eight mil

e made much better time, and we might then have been ne

uld have made better tim

then have been go

ion. Sailing ships travel faster when t

at the Professor

f the wind pushing sidewise could be more effective than a pressu

d is 1,000 pounds, it is estimated that fully half is lost in effectiveness. On the other hand, if the ship is moving forward at right angles to the direction of the wind, and the sail is set at forty-five degrees, that is what is cal

that the wind blows flat against it, the pressure

22. Illustrati

normal position. You will see the darts representing the direction of the movement of the wind. Now look at the next sketch (Fig. 22). Here the sail (B) is put at an angle of forty-five degrees from the direction of the wind. The sail is still the same size vertically, bu

sail normally, as you say, in what way do the

rred to. On the other hand, by examining the second sketch, the darts (2) plainly show their course across the sail diverted from their straight source, and behind the bulging sail the air does not press against the sail, but tries to co

es the air push just as hard against each square foot when i

ht ordinarily be overlooked. No, it does not,

g against it straight, as in the first sketch, at the rate of twenty

h square foot of surface is 2 pounds, and

degrees, what is the pre

is employed. A constant is a figure which never varies. In this case the constant is designated by the decimal .005. That means 5/1000th, or reduced to its lowest denomination, 1/200th. If, now, we d

en it is normal, what w

etter understanding, value, and the value at 45 degrees is .666. So that b

a great deal in flying

ursue, but there are some things right ahead

a quarter-hour sail, land was again espied ahead, so that to avoid the shore the course was taken due north. This was evidence that the land projected

id Harry. "What is the proper thing to

speed by an examination of the passing water, where the sea is comparatively calm. I have known where the distances have been thus estimated within a hundred feet in each mile in a ten-mile course, and where the speeds were varied along the route. Then,