fess to give the amount of the heat absorbed. This is what the theory of Latent Heat attempts to do, but what it cannot do till we have clear notions of the nature of heat. The formula now pro-posed gives us the temperature of a mass of water, into which a certain weight of steam has been condensed, or from which it has been abstracted. When there is no water, it is of course a contradiction in terms to enquire what is its temperature. But it may be said, that while there is yet any water left, we may conceive it to be less than any assignable quantity, in which case the reduction in temperature should be greater than any assignable number of degrees. Here the apparent paradox (if it be one) consists in this, that the depression of temperature is estimated with regard to a mass of water continually diminishing. Were it referred to an unvarying mass, the number of degrees would be finite. Besides it is obvious from the Table, that as the temperature sinks an increased proportion of steam is required to be abstracted, in order to reduce the temperature 10. This increase within the limits of the table is so considerable as to occasion an increase in the actual quantity of steam, notwithstanding the decrease of the mass to be cooled. For instance, if we take 10,000 grains of water, temp. 212°, the evaporation of about 79 grains will reduce the temperature to 200, of 80 more to 190, of 81 to 180, and so on, the quantity of steam increasing by unity for each decade of degrees. Whether this would continue to be the case at very low temperatures, we have no means of judging. If it did, the depression would be finite, even when estimated with regard to the continually decreasing mass of water. Add to this that when the temperature fell to 32°, there would be a change in the Law. What result this might produce I cannot prepare to show for want of experiments. But the objection is in reality fanciful, and in no way militates, when properly considered, against the truth of the formula, which being indeed an expression of the facts, may be received with every confidence.

*

POSTSCRIPT.

SINCE writing the above, I perceive by a paper of Dr. Thomson's, in the 3rd vol. of the Annals, p. 302, that the property of steam discovered by M. Clement, had been previously established by Mr. Sharpe, who found that 6 oz. of steam at 2120 and 275°, had equal heating power when condensed in water. Dr. Thomson has applied this fact to the illustration of the doctrine of latent

THIS department of science has been less cultivated than perhaps any other, and it is quite surprising how few are the practical results to be extracted from our best works. Each author seems satisfied to copy his predecessor indifferent as to the soundness or unsoundness of his views. The whole subject, as usually treated, is eminently hypothetical, and consequently full of error, while the student in vain seeks for those confirmations by experiment which the "Minister and Interpreter of Nature" should be prepared to furnish.

heat, and has given a table of the sensible and latent heats of steam at various temperatures. This table, when extended, leads to results (as pointed out by Mr. Herapatt in a paper in the same volume, p. 419), so very preposterous and absurd as appear to me to be conclusive, with regard to the value of this so much vaunted hypothesis. Mr. Herapatt shows, that if, as held by the support. ers of latent heat, the sensible and latent heats of steam form a constant quantity, then at 1228° Fahrenheit the latent heat will be 0, and if the temperature rise still higher, the latent heat becomes negative, i. e. water in becoming steam, gives out heat instead of absorbing it. Such a conclusion requires no comment.

H.

ART. III.-Observation of the Solar Eclipse of the 14th April," 1828, at Benares, in Latitude 25° 20' 14" N., and Longitude 5 31" 40′ East from Greenwich.

THE elements for the calculation of this Eclipse were as follows:

FROM these elements applied to the construction of a diagram, the following periods of the Eclipse were deduced:

Ben. Appt. Ti.

First appulse of the Moon on the East limb of the

Sun, 14° South,.....

Greatest Darkness,..

Conclusion, at West 1510 North,.

Diameter of the Segment remaining unobscured....

THE observations on the present occasion were conducted entirely with the small equatorial instrument to which allusion was made in the notice of the Lunar Eclipse in November last. The Telescope is by Dolland, and has a focal length of 15 inches, with an opening of 2 inches in the object glass.

THE Instrument being set up where no meridian mark could be obtained, was not accurately adjusted to traverse in the Equator, so that the horizontal wire of the field was found to make an angle of about 13 degree with the Sun's equatorial diameter.

It is necessary to mention this circumstance, because the measurements taken during the Eclipse have all reference to the enormous equator of the telescope, and the time occupied by the transit of the Sun's diameter past the vertical wires, from the obliquity of his motion, exceeded that given by the tables, and by the noon observation with the Transit Instrument, nearly half a second.

THE Commencement of the Eclipse was observed at Benares, apparent time 3 11 49'.6, and immediately afterwards a careful series of observations were made, on the passage of the cusps and tangent, or limb of the obscured segment over the 3 vertical wires of the telescope. The measurements are expressed in the accompanying table in horary seconds and fractions counted from the passage of the Sun's preceding limb, reckoning the Sun's diameter equal to 130.2 seconds.

THE time of observation given in the first column is not, as on former occasions, the moment of the passage of the Sun's centre over the middle wire in each case; but the mean moment of the several segmental passages only. This is evidently a more correct assumption, because where any sensible delay elapses between the mean of these and the central transit, a proportional advance of the segment for the elapsed time would require to be applied, and this becomes a very appreciable quantity near the beginning and termination of the Eclipse, since the Moon's limb advances on the Sun's disc, at the rate of nearly 1 second per minute.

TABLE,

THE Eclipse being at this time nearly advanced to the maximum obscuration, the noting of the transits was temporarily suspended, and a divided object-glass Micrometer was attached to the telescope, for the purpose of measuring, with accuracy, the diameter of the uneclipsed segment of the Sun.

THE divisions of the Micrometer had been previously examined and proved correct by measurements of the Sun's diameter.

THE difference between this result and the calculated measurement, namely 9 seconds is attributable partly to the irradiation which diminished the apparent diameter of the Moon, and partly to errors of the Moon's latitude, local parallax, and delineation; it is of trivial amount.

AFTER taking these measurements, the instrument was again adapted for continuing the transits, which were conducted in the same manner as before. There were several spots visible on the Sun, the first came into contact with the Moon's disc at 3h 58′′ 27. the second at 4h 09m 18'-the rest were not observed, nor were the emersions of these spots.