correct it; or, in case of there being none, to restore his confidence in his observations and final result. Mr. Scott's practice is to have the front side of his levelling-staff graduated from the bottom as usual, and painted in black and white; but, in addition, he graduates the rear-side of his staff, and paints it in red and white. This red graduation is in the subdivisions the same as the front one, but the position and numbering of the principal divisions are different: the first principal red division being made at 0.75 ft. from the lower end of the staff, and numbered III.; the next above, IV., and so on. Both sides of the staff are to be read off at each observation; and it is evident, that two very different heights of each observed point will be recorded; that from the red side being constantly 2.25 ft. higher than that from the black or the true one. A difference so wide, that the memory can never act disadvantageously in reading off the quantities on the two sides. An error in the levels can, by this mode of registering, be detected by a single glance; for the surveyor has simply to ascertain the place where any two observations of the same point have not the regulated difference. If no case of this kind occurs, there arises a feeling of confidence in the accuracy of the whole level-survey, which can scarcely be shaken.

EXPERIMENTS ON THE CIRCULATION OF THE BLOOD.

BY PROFESSOR HERING, OF Heidelberg.

FROM the very first hour that the circulation of the blood was suggested, to the present day,-during the period of doubt and examination which naturally followed its public announcement; and in spite, as it were, of the searching investigations of modern anatomy and physiology, not the slightest suspicion seems ever to have crept in, that the velocity of the circulation did not depend upon the rate of pulsation. No connexion of cause and effect appeared closer or more legitimate than this. Analogy furnished the most decisive instances to support it, when any were wanting; and the possibility of this connexion being dissolved, appears never to have entered the brain of any observer. That the pulsation of the heart and arteries, and the velocity of the circulatory motion, were at all times exactly proportionate,—that the heart was the agent, and its contraction was the only cause, of the sanguineous circulation; and that it acted upon the blood, as a forcing-pump does upon any other fluid, was the belief and the language of the greater number of physiologists of the past and of the present time. The simple denial of a fact so apparently true, and so generally admitted, if it came from a person of intelligence and veracity, would be startling; and the attempt to reduce it, at once to a vulgar error," would be considered quixotic and absurd. Professor Hering, either by acute observation, and true philosophic indifference to all theories, however old and extensively received, or by some accidental circumstances, has, however, suspected the truth of the notion; he has proceeded from suspicion to experiment, and has arrived at results which, to say the least, throw great doubt upon, if they do not entirely disprove, this supposed relation between the pulse and the circulation.

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The Professor, in his experiments, operated upon horses, generally in a healthy state. The animal was permitted to be free, in a proper place for the purpose, and the jugular vein on the left side was opened, and substances introduced whose effect was to excite respiration, and accelerate the pulse. When the acceleration had arrived at a certain point it was noted; an alkaline solution was then injected into the opposite jugular vein, and care taken to collect, every five seconds, specimens of the blood. The number of seconds which were necessary for this solution to travel through the system, from one jugular to the other, was considered a measure of the velocity of the circulation.

A series of forty of these experiments are recorded in the following table, with a statement of some of the means used.

The inspection of the preceding table will generally excite surprise, at the disproportion which it shows to exist between the rate of the pulsations and the velocity of the circulation. The circulation in its normal state, in a healthy horse, is completed in 20-25 seconds. But, taking into consideration all the circumstances of age, sex, and size, it may be considered as a general rule, that it requires 20-30 seconds to accomplish the circuit. In the forty experiments of the table, the velocity in three exceeds the mean, and the time is shorter than the rule; in fifteen, the time and the velocity are about the mean: and in the remaining twentytwo experiments, the velocity of the circulatory motion is more or less diminished, and the time consequently longer. In the thirty-fourth, the time was 90 seconds, or to speak more correctly, the circulation had nearly ceased.

The result drawn from these experiments by Professor Hering is, that the circulatory motion has no relation whatever to the number of pulsations. In confirmation of this opinion it may be observed, that in three pairs of the above experiments, the number of pulsations being the same, the times of circulation are different; in nine other pairs, the times of circulation are the same, but the number of pulsations is doubled; and in four pairs, where the times of circulation are the same, the pulsations are even trebled in number. Irregularities so great and varied as these, are far beyond the range of variation permitted by Nature, in any of her laws hitherto observed.

Further inquiries into this very curious subject are now evidently necessary; and probably it will not be long before the remarkable and apparently paradoxical discovery of Professor Hering will be confirmed, or his mistake, if he has fallen into one, be explained.

ON BORED WELLS.

THIS convenient, we may say elegant, method of obtaining good water from great depths, without the labour of lifting it, is spreading extensively in France, principally owing to the enlightened and patriotic exertions of MM. Arago and Hericart de Thury. The first, by his writings on the subject, and his successive notices of the works as they are executed, excites and keeps alive the attention of the whole French nation.

For the same purpose, with regard to our own country, we shall, at all times, be gratified by receiving and publishing, correct and detailed accounts of Bored Wells, executed in England, &c. Cases of supposed failure in these attempts, where all the circumstances are known, wouldbe as acceptable as those of success. Hints might be suggested for proceeding again with a prospect of arriving at the desired object; or, if this is hopeless, the facts might be recorded and useless expenditure prevented in future similar cases. In preparing the accounts, attention should always be paid to the kind of strata passed through, their thickness, &c. The locality of the well should be accurately described, its contiguity to river, mountain, sea, lake, &c., or the contrary. The waters of infiltration, (land-springs, &c.,) should be noted; and the supply, qualities, tempera

ture, and permanent elevation of the water finally obtained, should be very carefully observed and described.

In

Among the more recent instances of success in well-boring in France is one not far from the bank of a river, in a meadow belonging the Château de Cangé, about three miles from Tours. The water was found at 425 feet deep, and the supply is about 560 imperial gallons per minute. At Elbeuf, two wells, contiguous to each other and to the river Seine, have been bored to nearly 500 feet. They are remarkable for the volume, purity, and high temperature (61° Fahr.) of their waters. twenty-four hours after a storm, or violent rain, one of these wells becomes troubled, and its water issues turbid with clay or sand, precisely like that of the Seine after heavy rains. As the bore of this well proceeded, several lots of very minute eels floated out from it: many of them were caught alive and sent to Paris. A M. Dieu has lately announced to the French academy, that he is occupied in endeavouring to use steam-power as an agent in this art.

In a well lately bored in one of the abattoirs (public slaughterhouses) of Paris, the depths and thicknesses of the strata were carefully noted; and M. Arago himself examined the temperature of the water obtained: at 815 feet deep, he found it to be 68° Fahr. The engineer was prepared to have gone down to 1300 feet, but having pierced through the bed of chalk under which was found the water at Elbeuf, he desisted at the depth of 815 feet. From this depth the water rose to within 16 feet of the surface.

If now we look on the other side of the picture, and regard the failures in France, we shall find a case the most remarkable for the extent of area over which unsuccessful attempts have been made, in the valley of the Garonne. From Toulouse to Bordeaux little hope is now entertained of profiting by wells of this kind. At Toulouse, the bore was carried down about 780 feet, being 282 feet below the level of the Mediterranean, and abandoned after a cost of above 11007. At Agen, at the depth of 400 feet, a series of calcareous earths, &c., similar to what had already been passed, again commenced, and the undertaker gave it up in despair. In Bordeaux, they bored through strata, &c., very like what had been met with at Toulouse, and not having met with water at 670 feet, it was deemed useless to proceed. Four other bores in the neighbouring department of La Gironde, were also unsuccessful; in one only did water appear. These repeated failures have naturally indisposed the inhabitants of this quarter of France to further attempts. A considerable addition to the geological knowledge of this part of the kingdom has, however, been obtained; and among the facts collected by M. Boisgeraud, there is one result relating to the temperature of the earth, from 30 feet below the surface down to 340 feet, which deserves to be recorded. The mean of seven observations, each of twenty-four hours' duration, was found to be 23° Fahr. for each 100 feet of depth: an increase which accords with that which is generally admitted.

The first bored well executed in the empire of Russia, was recently and successfully completed at Riga.

A POPULAR COURSE OF ASTRONOMY*.

I.
INTRODUCTION.

THERE can have been no period in the history of mankind, in which they did not behold, with a desire to comprehend them, the changes which are daily taking place in the face of the heavens above them; and there can have been none in which they did not perceive these changes to sympathize with others in the surface of the earth around them. He who looks out upon the heavens, beholds a canopy spread forth like the half of a great sphere, of which he appears to occupy the centre. In the day-time, when it is of the colour of azure,—the hue of light in which his perception of its existence is most pleasant to him, the sun daily takes his course, in a zone, across this fair canopy, "like a giant that renews his strength." As night approaches, the curtain of the heavens gradually loses its transparent azure tint, becomes opaque, darkens, and at length it is black as sackcloth of hair; then come the millions of the stars, and are strewed like gems upon its surface; and in her season the moon walks forth in her brightness, and holds sway amid the dreary watches of the night. These daily changes in the heavens appear to have but little relation to the changes of vegetable life, but over the whole of the animated creation their power is absolute. The song of the birds becomes mute at nightfall, and again wakes only to welcome the returning sun. The beast lies down in the forest, the reptile crawls to his lair, and man himself sinks under the mysterious influence of the changing heavens; and returning to that state of oblivion out of which his birth first brought him, he stretches himself out to sleep. Such is the experience of a day. That of a year brings a still further knowledge of the wonderful sympathy between the changes in the heavens above him, and those in the things around him. He sees the sun not daily to describe the same path in the heavens, but at one time to travel obliquely across them in a higher, and at another time in a lower zone, so as at one time to have a longer course to run, and at another a shorter; and thus at one time to give him a longer, and at another a shorter day. This change in the elevation and consequent length of the sun's oblique path in the heavens, he soon perceives to be coupled with a change in his own perceptions of the intensity of heat and cold; when the sun's path is lowest or most oblique, he is colder than when it is highest. And not only do his own feelings sympathize with this change, but all nature around him. The hand that covered the beast of the forest with a coat of fur, now thickens its garment. The bird, whose path is free in the heavens, now guided by a spark of that intelligence whic called it into being, becomes conscious of the existence of a warmer sky in some remote unseen region of the earth, and seeks it. The green herb withers, the blossom dies, the leaf becomes sapless, and falls to the ground. Is it possible, that he who beholds all these changes around him, and who is thus deeply interested in them, who cannot but see that they are all bound together as by a chain, and * This course will be succeeded by similar ones on other subjects. VOL. I.

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