iS82.] Analyses of Books . 741 
vis viva ? He shows that supposing the velocity of the comet 
to have been 300 miles per second, then every 1 lb. of its mass 
would liberate heat enough to raise 126 tons of water from the 
freezing- to the boiling-point. But what will be the weight of a 
comet? Here authorities differ. Sir John Herschell thought “a 
few pounds.” The author thinks it “ improbable that the whole 
thing has a mass much greater than a few tons,” whilst Professor 
Pierce argues that the nucleus of the comet of 1843 must be of 
metallic density, and consequently that its mass must amount to 
thousands of tons. 
The meteoric train which the “Doomed Comet” — like 
every other body of its class — draws after it, is estimated at 
200,000,000,000,000,000,000 lbs. Were this quantity of matter 
suddenly plunged into the sun, the heat evolved would be suffi- 
cient to raise the temperature of a sphere of iron of the size of 
the earth to 1450° C. above its melting-point. Such a liberation 
of heat would doubtless affedt the radiation of the sun. But from 
considerations laid down it is probable “ that the comePmust be 
swallowed up piece-meal, the whole operation occupying not 
years but possibly centuries.” 
Turn we now to a consideration of the effects of increased 
solar activity upon the earth. The presence of sun-spots has 
for more than two centuries been supposed to influence the 
weather. But concerning the nature of this influence the learned 
are not agreed. Some have held that a spotty sun portends cold 
and wet ; whilst others maintain that it causes fruitful seasons. 
An increasing attention has been given to the subject since Wolf, 
of Berne, discovered the sun-spot cycle of eleven years, and con- 
cluded that when spots are plentiful the seasons are warm and 
dry, but when the sun is spotless they are cold and wet. 
The author does not dispute the connection of this cycle with 
the occurrence of magnetic storms and aurorae. But he is 
sceptical as regards its influence upon hot and cold seasons, 
cyclones, storms and gales, wet and dry seasons, frequency of 
hail and thunder, earthquakes, famines, pestilence, political 
agitation, the sweating sickness, the potato disease, commercial 
crises, and shipwrecks. He reminds us that Gautier, from ob- 
servations embracing Europe and America, came to a conclusion 
precisely opposite to that of Wolff, whilst Dr. Jelinck, from ob- 
servations embracing the whole world, shows that no conclusions 
at all can be drawn. He remarks : “ Statisticians, like the late 
Stanley Jevons, Mr. W. W. Hunter, and others, took it for 
granted that a connexion between the number of sun-spots and 
our meteorological conditions was established when nothing of 
the kind had been done. They constantly said ‘ meteorologists 
tell us ’ so and so, and then proceeded to argue upon the basis 
of Lockyerand Company’s statements. Shaky foundation ! Mr. 
Cornelius Walford’s chronology of famines has effectually dis- 
posed of the famine cycle, and works of a similar nature would 
