tation in the shape of snow or rain, which gives a remarkable coincidence. For in and during the past seven years there were 918 days on which rain or snow fell (this is regardless of the amount or duration), and during the like period there were 816 days on which ozone was present in a quantity of five tenths; any amount below that quantity in this estimation is not taken into consideration in the discussion. In the year 1850 there were 106 days of precipitation, and 110 days of ozone. The small amount of ozone in 1854, which was the year of the last visitation of cholera, would tend to favor the opinion that there was a deficiency of ozone in the atmosphere during the prevalence of that epidemic. A deficiency was, however, observed in almost every month of that year, although the number of days on which snow or rain fell were almost equal with the other years; for which see the following table, which shows the amount for each year, and for each respective month: Southerly and easterly winds being the point from which our rain or snow generally comes, are for the most part present, during the indications of ozone, while, on the contrary, northerly or westerly winds very rarely accompany its development. In reviewing these observations, there is no condition of the atmosphere appreciable. by our instruments, that indicates the presence of ozone, except the presence of vapor or humidity. Schonbein has asserted that a high electrical state of the atmosphere was always present when ozone was developed, and that the amount depended essentially on the amount of atmospheric electricity. From the comparison of nearly 6,000 observations on the electrical state of the atmosphere, and the amount of ozone taken at the same hour, at this place, and carefully compared, I have not found that opinion sustained, neither have I found its amount or presence influenced by the appearance of the aurora borealis, which has also been said to be the case. From these observations it would appear that a moist and humid atmosphere was necessary for the development of ozone, and this may account in some measure for its more constant presence and its greater quantity in proximity to the sea. So far as regards its effects on the production of disease in plants, especially the potatoe, and to which it has been more especially referred, it is almost certain that one of two causes must have given rise to the lamentable failure in this useful vegetable; either that the soil must have furnished the medium of disease, or the action of the atmosphere upon the leaves and stem of the plant; the causes which act upon the stem and leaves involve the action alone of atmospheric influences, while those that act through the medium of the soil are more numerous. In this neighborhood the disease showed itself after rain followed by a hot sun, the atmosphere being loaded with moisture or vapor, — just the condition essentially proper for indicating the presence of ozone,and the disease was much more extensive on wet and clayey soils than on sandy or dry ones. It cannot be doubted that an agent so active as ozone, if really present, must exert a great influence on the health of individuals, as well as animals and plants; the manner of its production, whether by chemical action or electricity or magnetism, demands from us further investigation, and these investigations should be carried out with uniformity for the sake of careful comparison, one point should not be overlooked, that is, to mark carefully the amount of vapor present in the atmosphere, as the intimate connection between them is too prominent to escape observation. I have, as you will perceive, offered no theoretical deductions. If, as our continental brethren assert, it does possess such powerful and wonderful properties, it must be evident that the American Association should at once take up the subject, in a way that we may arrive at important conclusions. I should not be justified in expressing a doubt on the labors of others in this department of physical science, neither do I think it fair to offer any conclusions until our observations are more extended; and it is with this intention that I have brought it before the Association, hoping that between now and our next meeting, we may be able to investigate and compare observations so as to give it a proper place in this department of physical investigation. 3. THE METEOROLOGY OF THE VICINITY OF MONTREAL. Prof. CHARLES SMALLWOOD, of Montreal, C. E. By I AM well aware that many of you are here for the first time in this, our northern city, and have scanned, and I have no doubt admired, the numerous edifices, those artificial structures erected by the human hand, guided by human skill, and well suited to our wants. I am also aware that many among you have bent your investigations beneath our alluvial and fruitful soil, to contemplate the geology of our rocky formations, and the deposits of by-gone ages, the work of that Divine Architect at whose command those bright and countless orbs that spangle in our firmament were brought into existence, and which form to the astronomer so many objects for his study; and I felt it might be interesting to you to know something of our climatology, and it is for this purpose I intend laying before the section some remarks in illustration, reduced from observations taken at St. Martins, nine miles due west of this place; and I shall for this purpose confine my observations to the means reduced from the last septennial period, al though the observations on record extend over a much longer period of time. The geographical coördinates of the place are 45° 32′ north latitude, and 73° 36′ longitude, west of Greenwich. The cisterns of the barometers are placed 118 feet above the level of the sea. The instruments used are standard instruments; the barometric observations are all reduced to the freezing point (32° F.), and the temperatures are all in Fahrenheit's scale. The hygrometric observations are reduced by the tables and formula adopted at the Greenwich Observatory in England. The receiver of the rain gauge is placed twenty feet above the soil. The direction and velocity of the wind are ascertained by a self-registering instrument, which indicates its velocity by dots on a paper register in miles linear. The electrical apparatus is provided with a collecting lantern, which is elevated eighty feet from the ground. The solar and terrestrial radiators are also read in terms of Fahrenheit's scale. The ozoneometer is of Schonbein's construction. The whole of the means are reduced from three daily observations, taken at 6 a. M., 2 P. M., and 10 P. M.; extra hours are also set apart for any unusual phenomena. - Barometer. -The mean height of the barometer for this period (seven years) was 29.676 inches; the mean reading for the same septennial period in January was 29.744 inches; February, 29.744 inches; March, 29.492 inches; April, 29.679 inches; May, 29.604 inches; June, 29.718 inches; July, 29.715 inches; August, 29.754 inches; September, 29.722 inches; October, 29.619 inches; November, 29.769 inches; December, 29.565 inches. The highest reading observed and on record here was on the 8th of January, 1855, and at 4 P. M. it attained the unusual height of 30.876 inches; the lowest reading on record was in December, also in 1855, and was 28.689 inches, giving an absolute range of 2.187 inches. The mean yearly range for the seven years was 1.032 inches, and for the months as follows:: There are two maxima and two minima variations occurring in the barometer in the 24 hours; the maxima variations occur at between 9 and 10 o'clock A. M., and between 9 and 10 P. M.; the minima variations occur at 3 A. M. and 3 P. M. Thermometer. The temperature of the air for the same period (7 years) exhibits a yearly mean of 41° 56′. The mean temperature of January was 13° 26'; February, 13° 31'; March, 25° 44′; April, 40° 12'; May, 55° 70'; June, 62° 11'; July, 74° 78'; August, 61° 21'; September, 58° 12'; October, 46° 04'; November, 31° 49′; December, 13° 80'. The absolute mean range for the same period has been from 90° 9' The absolute monthly range was, in to 27° 4′ +40° 7 to 25° 1 +94° 5 to 40° 5 + +97° 1 to 47° 8 + (below zero). +60° 4 to 5o 7 + +96° 7 to 40° 6 + 91° 2 to 30° 4 + +75° 7 to 23° 8 + The highest temperature in the shade on record here was 100° 1′, and the lowest was 36° 2' below zero; giving a climatic range of 136° 3'. The hottest month is July, and the coldest month is February. The warmest part of the day in summer is at 3 P. M., and in the winter season at 2 P. M. The coldest part of the day in winter is at a little before sunrise. The mean yearly temperature of the dew point reduced for the same period, was 35° 6', and for the different months as follows: :- The relative degree of humidity for that period, saturation being 1.000, was 814; and for the months: The elastic force of vapor exhibits a daily maximum at 3 A. M., and a minimum at between 3 and 4 P. M. The summer quarter, which |