the former unfortunately capsized, and three of the lifeboat men, the pilot, and eight of the shipwrecked crew were drowned, the remainder being rescued by the New Brighton boat. The services of our Liverpool lifeboat men were recognised by the United States Government through the Life-Saving Service in the most handsome manner, and the survivors of the crews of the two lifeboats, twenty-seven in number, were each presented with a gold medal of the first class, together with a letter of thanks from the Government of the United States. $200 were also awarded by that Government for the families of each of the three lifeboat men who lost their lives on that occasion.

The total expenditure of the Life-Saving Service for the year 1880 was $435,962 or about £89,889, and in the previous year $363,674 or £74,984.

In order to be able to form some comparison of the work done in the United States and in our own country for the preservation of life on the coast, I may state that the expenditure by the Royal National Lifeboat Institution during 1880 was £37,577, for which amount 271 lifeboats and stations were maintained. £1,800 voted for the support of the widows and families of lifeboat men who had perished in the discharge of their duty, and numerous rewards given for saving life by shore-boats and other means. 577 lives were saved by the lifeboats, 120 by shore-boats, &c., for which awards were granted, and 430 by the rocket apparatus worked by the Coastguard and the Rocket Volunteer Brigades, the cost of which service I have not been able to ascertain.

In conclusion, I only hope that this, I fear, very dry recapitulation of facts and figures may have been the means of impressing upon your minds that we are not the only people who endeavour to rescue those who are exposed to the perils of the deep, and to encourage you to support that noble

institution which in England supplies the place of a Government Life-Saving Service.

I do not wish to discuss the question whether work of this description is better undertaken by a Government department or by a charitable institution. Perhaps the truth is that, like the self-righting lifeboat and the surf-boat, each is specially adapted for particular localities, and in an enormous country like the United States, it would perhaps be impossible for a charitable organisation, depending for its support upon the populous cities, to organise and maintain a series of stations. over so large an extent of coast and one so thinly populated. At the same time it behoves us, residents in a small country like this, to remember that, densely populated as it is, there are scores of localities where lifeboats are stationed dependent entirely for their support upon the surplus subscriptions from large cities like Liverpool, and where the local subscriptions are entirely inadequate to support the station; and I trust that Liverpool will always be found one of the largest contributors to that institution which in England supplies the place of a Government Life-Saving Service.

ON THE VELOCITIES OF GASES.

BY ALBERT J. MOTT, F.G.S.

My object is to suggest a physical method by which the maximum molecular velocities of gases may be determined within certain limits.

Assuming the truth of the Kinetic theory, a gas is composed of molecules not resting in contact, but in constant and rapid motion in straight lines in all directions. There are other motions also, rotatory and vibratory, but it is the motion of direct translation in straight lines till something is encountered that is here considered.

The cause of this motion is heat communicated to the gas, or more correctly this motion itself is the sensible heat of the gas. In solids the molecules are held together by forces which prevent their heat motion from separating them. In gases these forces are absent or have been overcome, and the molecules, no longer held together by them, move independently under the influence of heat. Every gas has received this motion from some definite source, and the motion would be lost if it were not continually renewed. In a glass jar, for example, full of air, the gaseous molecules constantly beating against the sides of the jar would soon exhaust their motion; that is, the air would become colder and colder till it fell to the temperature at which it would cease to be gaseous, and would take a liquid or solid form. But the jar renews the motion as fast as it is wasted; the glass itself is heated, that is, also in motion, and though the motion in this case is vibratory and the glass molecules do not leave each other, they give back to the gaseous molecules

G

as great an impulse as they receive from them, the motion of the glass itself being maintained by other sources of heat, which we may finally trace back to the rays of the sun or the temperature of the earth.

But if a gas is not inclosed in anything, so that its molecules meet with no resistance except from their mutual encounters, the effect of their motion is to spread them. farther and farther apart, the gas thus expanding without limit unless some force acts upon it from without. And as it expands, and the distance between its molecules increases, their encounters become less and less frequent, till at last some of them, and finally all of them, tend to fly off along independent paths through space.

We never meet with empty space, however, and gases as we know them are always inclosed. Any given portion of air, for example, has the earth beneath it and other portions of air above and around it, and its moving molecules meet in every direction with something from which they receive fresh impulse and by which they are driven back.

In the atmosphere, however, while the earth below it makes a solid wall, the air above any portion of it makes a wall that can be more or less penetrated. This wall also becomes thinner and less substantial as we go higher, and at some upper limit there is no longer anything to meet and confine such of the molecules as are moving upwards. What then will happen to them? They will ascend to a certain height above the earth, and then fall back; the height to which they are carried being determined by the velocity with which they start and its relation to the force of gravity.

The actual velocity with which gaseous molecules move is determined in this way:

The normal pressure of the atmosphere downwards, on a square inch, at the earth's surface, is equal to the pressure of