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fine stem, and this only extending for a few degrees, corresponding to the range which may be supposed likely to be ever required. The thermometer which he has employed the most frequently has a scale of 3.98 inches to every degree of Fahrenheit, and has a thread of 22 inches. Upon comparison with the common barometer, it was found that a difference of 1° Fahrenheit is occasioned by 0-589 on the barometer; 30-603 on the barometer is equal to 213-367 on the thermometer; and 28.191 on the barometer is equal to 209.263 on the thermometer. The author gives a very minute description of the apparatus, and the mode of constructing it; from which we may conclude that every circumstance has been attended to which can contribute to its accuracy and convenience. The whole apparatus, consisting of the thermometer, the boiler, a stand, and a cover to protect it from the weather, is so contrived as to go into a tin cylindrical box, two inches diameter, and 10 deep, and weighs 1 lb. 4 oz. The experiments that Mr. Wollaston has hitherto been able to make with the new instrument afford a very convincing proof of its accuracy; the height of Shooter's Hill, of Hampstead, and of the top of St. Paul's cupola, agreeing with the estimates formed by Gen. Roy within a foot or two. Although the instrument is principally adapted for measuring only small differences of altitude, yet, by making a series of observations, and adjusting it after each experiment, by forcing up a globule of the mercury into a bulb that is left for this purpose at the top of the stem, it may be employed for ascertaining the heights of the highest mountains.

Sir E. Home's paper on the impregnation of the female in the class mammalia, a subject which had eluded the researches of the most eminent physiologists, and, among others, of Haller and Hunter, affords a valuable addition to our knowledge. He fortunately met with a case of a young woman who died seven days after her first and only sexual intercourse; and, having first hardened the uterus and its appendages in alcohol, it was minutely examined. One of the ovaria exhibited a small fissure on its most projecting part; and upon opening it he found "a cavity filled up with coagulated blood, and surrounded by a yellowish organized structure." Upon examining the cavity of the uterus itself, its inner surface was found to be lined with an exudation of coagulable lymph; and among the fibres of this lymph, near the cervix, the ovum was detected; it was of an oval form, one portion of it white, and the other semitransparent; but by the action of the alcohol the whole became opaque, The os tinca was closed with thick jelly, but the openings into the Fallopian tubes were pervious.

From this, and other analogous cases, the author has adopted an idea respecting the nature of the corpora lutea which is new, but for which he adduces some powerful arguments. The corpus luteum was supposed by Haller to be the effect of impregnation;

and as it follows from this view of the subject that actual impregnation takes place in the ovarium, many hypotheses have been formed to account for the manner in which the semen can pass along the Fallopian tube. The present writer, on the contrary, supposes that the corpus luteum is a compact glandular substance in which the ovum is formed, and that, from certain causes, it may pass into the uterus, where it is impregnated.

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The small ovum was given to Mr. Bauer, of Kew, in order that he might examine it by his microscope, and we are presented with a very minute account of its appearance. It is described as consisting of a membrane, comparatively speaking of considerable thickness and consistence, forming a kind of bag of an oval form, nearly of an inch long, and about of an inch broad: on one side it has an elevated ridge down its longest diameter, and on the other side it appears open for nearly its whole length, the edges of the membrane being rolled inwards, so as to give it something of the shape of a shell of the genus voluta. The outer bag contained an interior smaller bag, one end of which was nearly pointed, the other obtuse; in the middle it was slightly contracted, so as to leave two protuberances, which, it is conjectured, were the rudiments of the heart and head. These protuberances were formed by two little corpuscles, which were contained in the interior bag, and were enveloped in a slimy substance like honey. The paper is accompanied by some characteristic engravings from Mr. Bauer's drawings.

The object of Mr. Knight's paper on the expansion and contraction of timber is to show that this effect is principally produced by means of what is called the silver grain of the wood, a series of cellular processes, which are extended in the form of radii, from the central medulla of the tree to the bark. In a paper which was inserted in the Philosophical Transactions for the year 1801, he endeavoured to prove that the motion of the sap depends upon the action of these processes, as they are affected by the different degrees of heat and moisture to which they are exposed; and he has been confirmed in this opinion by many experiments and observations, which he has had an opportunity of making since that period.

The first set of experiments which he relates consisted in taking thin boards of oak and ash, which were cut from the tree in different directions with respect to the silver grain," so that the convergent cellular processes crossed the centre of the surfaces of some of them at right angles, and lay parallel with the surfaces of others." When both these pieces of wood were placed under similar circumstances, those which had been formed by cutting across the convergent cellular processes soon changed their form very considerably, the one side becoming hollow, and the other raised; and in drying, these contracted nearly 14 per cent. relatively to their breadth. The others retained,

with very little variation, their primary form, and did not contract more than 3 per cent. in drying."

Mr. Knight's second experiment consisted in taking a transverse section, of about an inch in thickness, from the stem of a tree that was just felled. An incision was then made with a saw from the bark towards the central medulla, in the direction of the convergent cellular processes, when they were found almost entirely to prevent the action of the saw in consequence of their expansion; and when a second incision was made from the bark to the medulla, about an inch from the first, leaving a triangular wedge, the expansion of the silver grain kept the piece closely retained in the stem. When incisions were made in the other part of the block, but in such a direction as to cut the processes across, the saw was found to move with perfect freedom. From these facts the author was led to infer that the medullary canal must be subject to have its diameter considerably affected by variations in the quantity of moisture contained in the wood; and this conjecture seemed to be confirmed by an experiment, in which a plug of metal forced into the central space, which had been occupied by the medulla of a young stem, while this was in a dry state, was found too small to fill the cavity, when the stem was saturated with moisture. Mr. Knight conceives that the internal clefts which are frequently met with in timber may be produced by this kind of expansion and contraction; a cause which he conceives more likely to operate than either winds or frosts, to which they have generally been attributed. Another cause by which timber becomes warped in drying is pointed out, which has probably no connexion with the power by which the sap is raised in the living tree, but which arises from the greater or less solidity of the different parts of the trunk, according as they are nearer or more remote from the centre, the former being more compact, and of greater specific gravity, and therefore being less affected by the evaporation of its moisture.

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Dr. Davy's observations, which were made during his voyage to Ceylon, were principally confined to three topics: cific gravity of the water of the ocean, and its temperature, and the temperature of the atmosphere." He first presents his principal results in the form of a table, and he afterwards informs us how they were obtained, and offers various remarks concerning them. The table consists of 13 columns: the first contains the date; the second, the latitude by observation; the third, the longitude by the chronometer; the fourth is the specific gravity of the sea water; the three next columns relate to the temperature of the air, its maximum in the course of the 24 hours, its minimum, and its mean; the next three columns give us the maximum, the minimum, and the mean temperature of the sea water; the 11th column contains the register of the

barometer; the 12th, of the winds; and the last, the account of the weather generally. The observations were continued, without much interruption, from the middle of February to the middle of August, when the author arrived at Ceylon, commencing in the 49th degree of north latitude, and 6 degrees west longitude, and proceeding round by the Cape of Good Hope and the Isle of France. The experiments on the density of the sea water were made on portions of water drawn from the surface of the ocean, its temperature being reduced by calculation to 80°, a number which was fixed upon because it is nearly the mean annual température of Ceylon, and of the sea generally in the intertropical regions. The results of these experiments show that the ocean resembles the atmosphere with respect to the general uniformity of its composition, the specific gravity of the water being very nearly the same in all the different trials. The number of observations recorded is 36; the highest specific gravity is 10277, and the lowest 12051. These variations seem to have no connexion with the temperature, or at least not to bear any regular proportion to it. The differences seemed rather to depend upon what may be regarded as incidental circumstances, as the roughness of the surface, a heavy fall of rain, and a succession of tropical squalls. Dr. Davy's observations controvert an opinion which has been adopted, that the different zones of the sea have each their peculiar specific gravity.

With respect to the temperature of the air and water, the observations were made every two hours with delicate thermometers. Dr. Davy conceives that the temperature of the atmosphere in hot climates has been frequently overrated from the thermometer not being sufficiently protected from the radiation of caloric by neighbouring bodies. The highest temperature that is noted is 82°; this occurred at 2° 10' north latitude, about five days before they arrived at Ceylon; the uniformity of the temperature in these regions is very remarkable, the maximum and minimum not differing more than 3° or 4° in ordinary cases, and seldom more than 5° or 6°. The author has made an observation on the diurnal variation of the temperature of the atmosphere at sea which had not been before noticed, which, when the weather is fine, and the wind steady, appears to have few exceptions: the air was "at its maximum temperature precisely at noon, and at its minimum towards sun-rise. But many circumstances were found to disturb the regular progression: on the one hand, in a perfect calm the accumulation of heat, not only in the ship, but in the water itself, cause the greatest heat to occur some time after the hour of noon, and by showery and unsettled weather the regular variation was still more disturbed.

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Contrary to what is commonly asserted, the diurnal change of temperature in the sea is very nearly as great as in the atmosphere. When there were the fewest disturbing causes, the weather fine, the surface smooth, and no land near, the

fine stem, and this only extending for a few degrees, corresponding to the range which may be supposed likely to be ever required. The thermometer which he has employed the most frequently has a scale of 3.98 inches to every degree of Fahrenheit, and has a thread of 22 inches. Upon comparison with the common barometer, it was found that a difference of 1° Fahrenheit is occasioned by 0-589 on the barometer; 30-603 on the barometer is equal to 213-367 on the thermometer; and 28-191 on the barometer is equal to 209-263 on the thermometer. The author gives a very minute description of the apparatus, and the mode of constructing it; from which we may conclude that every circumstance has been attended to which can contribute to its accuracy and convenience. The whole apparatus, consisting of the thermometer, the boiler, a stand, and a cover to protect it from the weather, is so contrived as to go into a tin cylindrical box, two inches diameter, and 10 deep, and weighs 1 lb. 44 oz. The experiments that Mr. Wollaston has hitherto been able to make with the new instrument afford a very convincing proof of its accuracy; the height of Shooter's Hill, of Hampstead, and of the top of St. Paul's cupola, agreeing with the estimates formed by Gen. Roy within a foot or two. Although the instrument is principally adapted for measuring only small differences of altitude, yet, by making a series of observations, and adjusting it after each experiment, by forcing up a globule of the mercury into a bulb that is left for this purpose at the top of the stem, it may be employed for ascertaining the heights of the highest mountains.

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Sir E. Home's paper on the impregnation of the female in the class mammalia, a subject which had eluded the researches of the most eminent physiologists, and, among others, of Haller and Hunter, affords a valuable addition to our knowledge. He fortunately met with a case of a young woman who died seven days after her first and only sexual intercourse; and, having first hardened the uterus and its appendages in alcohol, it was minutely examined. One of the ovaria exhibited a small fissure on its most projecting part; and upon opening it he found " cavity filled up with coagulated blood, and surrounded by a yellowish organized structure." Upon examining the cavity of the uterus itself, its inner surface was found to be lined with an exudation of coagulable lymph; and among the fibres of this lymph, near the cervix, the ovum was detected; it was of an oval form, one portion of it white, and the other semitransparent; but by the action of the alcohol the whole became opaque, The os tinca was closed with thick jelly, but the openings into the Fallopian tubes were pervious.

From this, and other analogous cases, the author has adopted an idea respecting the nature of the corpora lutea which is new, but for which he adduces some powerful arguments. The corpus luteum was supposed by Haller to be the effect of impregnation;

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