180 M‘Sweeny, on the Climate of Ireland. 
Shannon, and knowing the effect of insular situation on climate, he could have no 
doubt on the subject. 
Mr. Daniel, in one of his meteorological essays, compares the Caspian sea, which has 
no outlet for the rivers which it receives, with the lakes of another continent, North 
America, which send an immense volume of water to tle ccean; he considers them 
as hygrometers on a large scale, by which we may judge of the state of saturation of 
the two atmospheres. Jn Ireland we have also a hygrometer on a large scale, we 
have the Shannon, an index of the large quantity of rain that annually falls. The 
fact of this fine river being in so small an island, “spreading like a sea,” as the poet 
Spencer described it, is alone quite sufficient to prove the great humidity of the cli- 
mate of Ireland. 
As the causes of climate here glanced at, are of a permanent nature, and as the 
laws of nature are immutable, it is just to, suppose that mildness and humidity were 
the characteristics of this climate always, when compared with the climate of other 
countries of Europe. The effects of draining and cultivation on climate, have been 
noticed in every quarter of the globe ; it would be strange if draining and cultivation, 
which have gone on rapidly with an increasing population in this island, have not pro- 
duced some effect on its climate. We will have to investigate in the course of this 
essay, whether Ireland be an exception to a general rule in this particular. Before 
entering on the task of tracing the history of the climate, it may be right to make 
some observations on climate in general, and to examine the assertion so boldly made, 
that the climate of Europe has greatly changed since the time of the Roman dominion. 
Our knowledge of different agents, such as heat, light, and electricity, is yet limited, 
their mode of operation is not sufficiently understood, to enable us to speak decidedly 
on several meteorological points. The nature of the sun itself is only surmised, the 
question of its being a habitable globe, surrounded by a phosphorescent atmosphere, 
or of its being a body of fire, is one that admits of discussion. amples are 
undecided about the nature of the solar spots; the question of their producing": any 
effects on the weather is yet involved in doubt. 
To Franklin we are indebted for the knowledge of the agency of electricity in the 
clouds. Scheele pointed out the action of solar light in blackening the nitrate of 
silver, but to modern research we owe the knowledge of the connexion between 
light, heat, electricity, and magnetism. The curious effect produced by light on a 
mixture of chlorine and hydrogen, excited attention, and the discovery of the pola- 
risation of light by Malus, directed the first philosophers of Europe to the subject of 
light. The action of the violet rays in exciting the magnetic influence, noticed by 
Morichini, and the connexion between electricity and magnetism, discovered by 
(Ersted, have opened a new field for inquiry, which has been cultivated with 
assiduity and success. 
The connexion between heat, light, electricity, and magnetism, fortunately, is en- 
