ADDRESS. lxi 
velocity of projectiles. This instrument has been of great value in recent 
investigations, and there are questions affecting projectiles which we can 
only hope to solve by its assistance. Experiments are still required to clear 
up several apparently anomalous effects in gunnery, and to determine the con- 
ditions most conducive to efficiency both as regards attack and defence. It is 
gratifying to see our Government acting in accordance with the enlightened 
principles of the age by carrying on scientific experiments to arrive at know- 
ledge, which, in the arts of war as well as in those of peace, is proyerbially 
recognized as the true source of human power. 
Professor Tyndall’s recent discoveries respecting the absorption and radi- 
ation of heat by vapours and permanent gases constitute important additions 
to our knowledge. The extreme delicacy of his experiments and the remark- 
able distinctness of their results render them beautiful examples of physical 
research. They are of great value as affording further illustrations of the 
vibratory actions in matter which constitute heat; but it is in connexion with 
the science of meteorology that they chiefly command our attention. From 
these experiments we learn that the minute quantity of water suspended as 
invisible vapour in the atmosphere acts as a warm clothing to the earth. The 
efficacy of this vapour in arresting heat is, in comparison with that of air, 
perfectly astounding. Although the atmosphere contains on an average 
but one particle of aqueous vapour to 200 of air, yet that single par- 
ticle absorbs 80 times as much heat as the collective 200 particles of air. 
Remove, says Professor Tyndall, for a single summer night, the aqueous 
vapour from the air which overspreads this country, and you would assuredly 
destroy every plant incapable of bearing extreme cold. The warmth of our 
fields and gardens would pour itself unrequited into space, and the sun would 
rise upon an island held fast in the grip of frost. Many meteorological phe- 
nomena receive a feasible explariation from these investigations, which are 
probably destined to throw further light upon the functions of our atmosphere. 
Few sciences have more practical value than meteorology, and there are 
few of which we as yet know so little. Nothing would contribute more to 
the saving of life and property, and to augmenting the general wealth of the 
world, than the ability to foresee with certainty impending changes of the 
weather. At present our means of doing so are exceedingly imperfect, but, 
such as they are, they have been employed with considerable effect by 
Admiral FitzRoy in warning mariners of the probable approach of storms. 
We may hope that so good an object will be effected with more unvarying 
success when we attain a better knowledge of the causes by which wind and 
rain, heat and cold are determined. The balloon explorations conducted 
with so much intrepidity by Mr. Glaisher, under the auspices of the British 
Association, may perhaps in some degree assist in enlightening us upon 
these important subjects. We have learnt from Mr, Glaisher’s observations 
that the decrease of temperature with elevation does not follow the law pre- 
yiously assumed of 1° in 300 feet, and that in fact it follows no definite law 
at all. Mr. Glaisher appears also to have ascertained the interesting fact 
that rain is only precipitated when cloud exists in a double layer. Rain- 
drops, he has found, diminish in size with elevation, merging into wet mist 
and ultimately into dry fog. Mr, Glaisher met with snow for a mile in 
thickness below rain, which is at variance with our preconceived ideas. He 
has also rendered good service by testing the efficiency of various instruments 
at heights which cannot be visited without personal danger. 
The facility now given to the transmission of intelligence and the inter- 
change of thought is one of the most remarkable features of the present 
