M‘Sweeny, on the Climate of Ireland. 219 
the country in general gets more good, than hurt by it ; and when any dearths fall out 
to be in Ireland, they are not caused through immoderate heat and drought as in most 
other countries, but through too much wet and excessive rain.” 
In 1826 a famine was apprehended in Ireland, yet the potatoe crop turned out much 
better than could be expected after so very dry a summer. 
In the Phil. Trans. No. 220, there is an account of a substance resembling butter, 
noticed in Ireland in November, 1695. A similar substance was remarked on grass 
in the autumn of 1826. The country people employed it to grease the wheels of 
carts. 
Boate remarked, that often in Ireland after days of rain, the nights were fair and 
clear ; the writer of this essay has frequently made a similar observation. 
The researches of Doctor Wells explain the formation of dew; the cloudy sky of 
Ireland interferes with radiation, and is one of the chief causes of the mild tempera- 
ture of our nights. Boate fell into an error, when he stated that there was as much 
dew in Ireland as there was in hotter and drier countries ; but he may be refuted by his 
own words—“ It is found ordinarily, that in a clear night following rain, the which is 
very ordinary, the dew cometh as liberally, as if it had not rained the day before.” 
But the nights in Ireland are not in general so clear as the nights in drier countries ; 
and Boate remarked that before rain, little or no dew was to be found, and he described 
the climate as subject to rain, therefore the formation of dew must have been fre- 
quently interfered with. His words are—‘‘ When it is towards any great rain, little 
or no dew doth fall.” In another part he observes—‘‘ We have showcth how much 
Ireland is subject to rain, and it is likewise to dark weather and overcasting of the air, . 
even when it raineth not, which continueth sometimes many days together, especially 
in winter time.” 
In Kirwan’s work on the Temperature of Different Latitudes, under the head of 
Stockholm, we are informed that Wargentin, in examining a series of 39 years, could 
not find that any one year resembled another... When a person examines the details 
of the years such as they are registered in Ireland, he sees such a variation, that he 
_ must be convinced of the folly of attempting to draw precise conclusions, unless he 
had a series of accurate observations made in the same place for a very long period. 
Thus if the seasons go through a cycle of fifty-four years, he should have observations 
for 108 years, to be able to compare two cycles. 
Mr. Howard, in treating of the mean temperature of London, observes: ‘ The 
mean temperature of the year is found to vary in different years to the extent of full 
four and a half degrees, and this variation is periodical. The extent of the periods for 
want of a sufficient number of years of accurate observations cannot at present be 
fully determined, but they have the appearance of being completed in seventeen 
years.” 
He ventured to make predictions of some succeeding years, and he has failed. 
VOL. XVII. 3B 
