chucked on the lathe, and bored out before shrinking on the wheel.

It is apparent that a machine of this description becomes applicable to tires of any diameter, by having three or four sizes of segments adapted to the table. It is found to diminish the manual labour, and to prepare the tire more accurately than by the usual process.

A model of the machine, and a detailed drawing of the several parts, accompanied the communication.

“On the improvement of the Roads, Rivers, and Drainage, of the Counties of Great Britain."

By Robert Sibley, M. Inst. C. E.

The author had on a former occasion drawn the attention of the Institution to the subject of a Bill before Parliament, "for the better regulation and general improvement of the Drainage of the Country;' and at the same time pointed out the course pursued by the magistrates of the County of Middlesex, in procuring with his professional assistance, an accurate account of the Rivers, Bridges, &c., hoping that it might lead to similar surveys in other counties.

In the present communication he investigates the nature of the works which each county may be expected to undertake, and the means of accomplishing them economically, so that real public benefit may accrue.

The objects principally requiring the attention of the county magistrates, he considers to be, First-Facility of intercourse by the improvements of the roads, bridges, rivers, and canals; Secondly-Protection from injury by the passage of the waters from or through the county; and Thirdly-The removal of causes tending to vitiate the atmosphere, or to render unwholesome the water used for the support of human life.

All these points, which do not appear to have been fully com

prehended in the Sewage Acts, are examined at length, and suggestions are offered for their regulation, with examples of the effects resulting from their neglect.

The advantage of placing the water-courses of the country generally under a well-regulated system of management, is insisted upon as the most effectual mode of guarding against the destruction of property, and not unfrequently of human life, which ensues from the effects of sudden inundations, such as have recently occurred in the county of Middlesex.

Original Communication.

ON THE ENGINEERING OF THE ANCIENT

EGYPTIANS.

BY J. S. PERRING, ESQ.

MANY YEARS A RESIDENT IN EGYPT.

No. IV.

We now propose to consider the most interesting monuments of antiquity, and which alone of the celebrated seven wonders have remained. The Pyramids,-mysterious records of man's early power; enduring for countless ages; undestroyed and indestructible by time; speaking of mighty generations long since passed away, and of their monarchs, the memory of whose very existence, save for the testimony of these unrivalled edifices, would have been lost in the obscurity of the infancy of time.

All the ancient authors (with the single exception of Homer) speak of the Pyramids, and vaunt their magnitude and antiquity; but their accounts furnish us with but scanty and doubtful information, for the erection of these eternal monuments belongs to an era too remote for history to record.

Until lately, the very object for which they were erected was involved in doubt; and the engineer alike searched ancient record, and looked at modern observation, without obtaining any

real information. Innumerable theories on their design and character have been formed, without any data that could be depended upon, and of consequent learned and useless discussion there has been a sufficiency.

The last five years have, however, furnished an ample stock of valuable information; and the indefatigable researches and brilliant discoveries of Colonel Howard Vyse, enable us to reason with some certainty on these wondrous structures. These discoveries are of the highest interest, and guided by them we proceed to examine some of the evidences of design shewn in the erection of these vast edifices, and to prove the constructive ability of the builders.

It is no part of our present object to enquire, whether the pyramidal form itself may or may not have been sacred, and owes its origin to its resemblance either to an ascending flame or descending rays of the sun; but, as the practice of raising a mound of earth over their illustrious dead, seems to have been universal amongst early nations, we may perhaps more safely ascribe the erection of Pyramids to a desire to form a more permanent memento of hewn stone.

And no better shape could have been adopted for eternal duration; it resists all external causes of decay, and contains no elements of destruction within itself. All oblique pressure is avoided, and the simple weight of the superstructure equally distributed over the whole area of base.

The proportions of these monuments have been supposed to have reference to the peculiar tenets of the Egyptians, in connection with certain celestial bodies; but if so, all erected near the same place, and about the same period, should have the same proportions. The Pyramids of Gizeh, we are assured by all ancient authors, confirmed by modern research, were erected within a short period of each other; yet Sir John Herschel gives his opinion, that the angles of the passages "differ too much and too irregularly to admit of any such conclusion;" nor was the exterior angle of these buildings "connected with any astronomical fact, and probably adopted for architectural reasons."*

The only point on which there is a perfect correspondence in all the Pyramids of Egypt, (except one,) is in their position with regard to the cardinal points, opposite to which their faces are placed; and the exact manner in which this is done, speaks much for the correct observation and true astronomical knowledge of the Egyptians.

If then the shape or proportions of these monuments have not been dictated by astronomical relations, to what are we to ascribe it? Sir John Herschel, a very competent authority, considers

* Vide Col. Vyse's "Operations,” Vol. II., p. 108. VOL. XIX.

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they have not, but that the shape was probably dictated by chitectural reasons;" that is, either from a wish to obtain the most solid and enduring shape, or from certain notions of symmetry.

Their present state shows that durability was effected, and that skilfully; for in the great Pyramid of Gizeh, nearly 480 feet in perpendicular height of solid masonry, the pressure of the enormous mass is so distributed, that the lower courses have only to sustain about 25,000 lbs. per square foot, whilst the material of which the building is erected is equal to at least 1,110,000 lbs.

The proportion that seems to have regulated the exact form of the great Pyramid of Gizeh, and of several others in Egypt, seems to have been a ratio of height to side of base, as 5:8, and this gives the following proportions on a direct section :-As half the base perpendicular height: the apothême or slant height the whole base. Or, for each side, it may be thus stated:-As Rad. Tang. :: Sec. 2 Rad."*

From finding, in every case, that the angles are thus regulated, we come to the conclusion, that the Egyptians, at the time of the erection of these mighty monuments, possessed no knowledge of a division of the circle per se, but that their angles were regulated by the proportion of base to perpendicular height; in fact, the tangential measure of the angle, but not its abstract admeasurement. That they learned to divide the circle into degrees at a later period, is highly probable, as they were celebrated for their astronomical knowledge.

Our space does not here allow us to pursue this subject further; nor is it within the scope of these papers to furnish a description of the Pyramids themselves; yet we cannot avoid endeavouring to convey some slight notion of the magnitude of the great Pyramid of Gizeh.

The space originally covered by it, appears to have been & Egyptian jugera or acres, equal to rather more than 131 English acres. The total contents of solid masonry 89,418,806 cubic feet, weighing 6,878,369 tons; but, as these quantities are difficult to be apprehended, we will endeavour to give some data, whereby a comparison with known objects may be established.

New London Bridge is perhaps the largest and most magnifi

*Mr. Agnew is of opinion, that " the Egyptians sought, in the appropriate figure of the Pyramid, to perpetuate, at the same time, a portion of their geometrical science;" and that in the third Pyramid of Gizeh, the "perpendicular height was the radius of a circle, the circumference of which was equal to the square of the base;" in fact, that the Egyptians, 4000 years ago, had practically solved the celebrated problem of the quadrature of the

circle !

For this, vide Plans, &c., of the Pyramids, lately published by Frazer and Weale.

cent single work of the present age; but there is sufficient stone in the great Pyramid to erect 57 edifices of the same magnitude.

A railway, laid on blocks, requires 14,000 cubit feet per mile, consequently there is sufficient stone in this building to lay a substantial railway 6387 miles, or round more than a fourth of the circumference of this globe at the equator, or a double line from hence to the Pyramid itself.

In collieries, a 12-horse steam-engine is considered necessary to draw 100 tons of coals per day from a 30 fathom shaft, therefore it would require the active services of 9 engines of 10-horse power each, for 20 years, to lift the materials from the plain, at the foot of the hill on which the Pyramid stands, to the level of the height required; but this only gives the power for lifting each stone to the level of the bed it was to occupy, and does not comprehend the extra power required to convey it to its exact situation.

About two-thirds of the stones, composing the Pyramid, were drawn from the vicinity, the average distance being about half a mile; a considerable portion of the remainder were brought from the quarries at Tomah, a distance of 11 miles; and a small quantity of granite, for the construction of the principal apartment and portcullis, from Essouan.

Supposing a good level turnpike-road had been formed from these quarries to the Pyramid, and well-constructed wheel-carriages used thereon, the services of 450 horses would have been required for 20 years to draw the materials. Or still further, supposing good modern railways to be laid between the same points, the active services of three powerful locomotive engines, working at 8 miles per hour, would be required for 20 years for the same purpose.

From the quarries of Tomah were drawn the blocks of the greatest consequence; they are situated about 11 miles from the Pyramids, on the opposite or Arabian side of the valley, the distance between them and the Nile being about a mile and a half. The stones were obtained from the quarry by being split off, the size required, by rows of wedges, the thickness of the strata determining the thickness of the blocks; and on re-opening these quarries, by order of the present Pacha of Egypt, in 1837, the author found in them sufficient evidence to shew that the ancient Egyptians fully understood and appreciated a systematic division of labour. The arrangement and unfinished work of the quarry shewed that five different gangs of workmen were simultaneously employed on as many different operations, the one gang preceding the other in the following order :—

At first the rock was cleared of the rubbish and levelled; then, on the surface, thus prepared, another set of workmen marked out, by a cut, a couple of inches deep, the stones re