4. " On Ground-gru, or ice formed, under peculiar circumstances, at the bottom of running water." By James Farquharson, LL.D., F.R.S., Minister of the Parish of Alford.
The author brings forward in this paper several recent observa- tions on the formation of ice at the bottom of rivers, the conditions of which corroborate the views regarding the cause of that pheno- menon, which he presented in a paper on this subject, published in the Philosophical Transactions for 1835 (p. 329), namely, that it occurs in consequence of the loss of heat by radiation from the bot- tom of the water, in a manner precisely analogous to the formation of hoar-frost on the surface of dry land, as first explained by Dr. Wells. He then answers some of the objections to that theory pro- pounded in an article, under the title of Ground-Gru, in the Penny Cyclopaedia, and shows that those objections are founded in error, and possess no validity.
5. " Meteorological Observations made at the Magnetic Observa- tory at St. Helena, from February to October 1840." By Lieut. J. H. Lefroy, R.A.
6. " Meteorological Observations made at the Magnetic Observa- tory at Toronto, Upper Canada, from January to October 1840." By Lieut. E. J. B. Riddell, R.A.
7. "Observations on Magnetic Direction and Intensity made at the Observatory at Milan during the 24th, 26th and 27th of January 1841." By Prof. Carlini.
8. " Note on an irregularity in the Height of the Barometer, of which the argument is the Declination of the Moon." By Sir John Wniiam Lubbock, Bart., V.P. and Treas. R.S.
In the Companion to the British Almanac for 1839, the author inserted some results which were obtained with a view of ascertain- ing the influence of the moon on the barometer and on the dew- point. Mr. Luke Howard's researches on this subject having re- called his attention to that paper, he found that some of the results he had given appeared to indicate that the moon's position in decli- nation influences the barometer. In order to render this more ma- nifest, he combines in the present paper all the observations he gave in the Companion to the British Almanac in three categories. These observations correspond to dift'erent angular distances of the moon from the sun, or times of transit ; but as the inequality of the ocean, of which the argument is the moon's declination, is independent, or very nearly so, of the time of the moon's transit, it is probable that so also is that in the height of the barometer. In this case we may with propriety combine in the same category observations which correspond to similar declinations, although to dift'erent times of transit. The results stated by the author seem to indicate an ele- vation of nearly one-tenth of an inch for 17 degrees of declination.
