1S42 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



.'50 



I 



and experience that the best metliod could be arrived at ; lie wished 

 that each student should, in his private study, well consiik'r, and, by 

 reading, tost the correctness of the principles which he laid down fur 

 their guidance. A whole year's lecture, repeated every day, would 

 be no more than sufficient to draw the attention of the student to im- 

 portant points — the details could only be gained by practical experience, 

 in preparing the foundation of lighthouses, the whole resources of the 

 engineer must be called into action. A lighthouse must be built in 

 such a manner that it must actually grow from the rock; there are in- 

 stances where lighthouses have fallen in a body. He could mention 

 one in Ireland, the foundation of which was a solid rock ; he saw a 

 party who witnessed its fall, and who informed him that it fell in a 

 solid mass, tearing away a portion of the rock with it. The fault was, 

 that the foundation was not sunk deep enough into the rock. He 

 then alluded to the celebrated Pharos (of Pharos) of Alexander, which 

 was justly reckoned one of the seven wonders of the world ; it was 

 built about 2>3 vears B.C., and received its name from the island on 

 which it was built ; it was TijU feet high, and the base was 150 feet 

 square, and could be seen at a distance of lU English miles. Josephus, 

 and many other authors, had given descriptions of it, which pretty 

 well agreed : and what was most extraordinary, that the very same 

 method of making the foundation was jiractisod then as now. The 

 stones were dovetailed together, dowellcd, and run with lead, so as to 

 firmly secure them in their places. The cost of the building amounted 

 to no less a sum than 200,(X)U/. of our money, and it lasted above l(j 

 centuries; no iliminution in its height occurred until after a 1000 

 years from its erection, at which time about one-third of its height 

 was wasted awav by time, and it Wiis only within about tOO years that 

 the whole is supposed to have been destroyed, and that only by means 

 of an earthquake. He then remarked, that it was very seldom that 

 the name of an engineer was handed down fur 2UOO years, but all ac- 

 counts agreeil that Sosastros was the name of the engineer who erected 

 this wonder of the world. The celebrated Corduan, or, as it is gene- 

 rally called, Cordovan Lighthouse, at the mouth of the Garron, is 

 built upon the same principles .is the Pharos; this lighthouse is, how- 

 ever, circular, but the masonry is not calculated for durability, it being 

 built of freestone. The expense of this lighthouse was enormous, as 

 must be supposed, when millions of francs were expended upon orna- 

 ment, which was the more aljsurd, when it was considered that it 

 stood upon a barren rock, in the middle of the sea. He could not help 

 quoting a line of Pope — 



'Tis only usefulness that sanctifies expense. 

 This is a sentiment that he wished to impress upon the minds of all 

 his students, for it was a great fault of modern engineers to expend 

 great sums upon ornament, which could be far better employed U])on 

 actual necessaries. He then turned to the Eddystone Lighthouse, and 

 related the histories ami fates of the two lighthouses preceding the 

 one now standing, which was erected by the genius of .Smeaton, and 

 strongly recommended his pupils to read the account published of that 

 great work. The Eddystone rock is peculiarly interesting to the en- 

 gineer ; it is found first at about one mile deep in the ocean, and then 

 rises gradually about one foot in ten, until it reaches near the level of 

 the sea, when a sudden crop makes its apjiearaiice, and rises above 

 surface. From the )ieculiar formation of this rock, there is always a 

 heavy run upon it, which renders it so verv dangerous. The learned 

 Professor, after explaining at some length the process of the erection 

 of this celebrated lighthouse, concluded his lecture. 



ON EARTH WORK. 



Lecture .'. Wednesday, 2-2nd December, IS 11.— The Professor com- 

 menced by stating that earthwork, taken in the present extended sense 

 of the word, was but little known to the ancients. The gigantic opc- 

 raticjns in earthwork ol modern times corresjiond with the viaducts of 

 the ancients. Our earthwork may be confined to excavation, cutting, 

 and cmbanknieiit, or getting and 'filling, as ordinarily denominated bv 

 contractors, lie then went through the whole process, giving the 

 s.ientifir and common names of each description of work. With 

 respect to the works of the ancients, in the canal made bv Cyrus, the 

 Pha-niciaiis were the only workmen who cut the canal with slopes — all 

 the rest employed cut straiplit down, and, in consequence, the former 

 stood, while the latter fell in. The River I'o, in Italy, was a curious 

 instance of enihankinent ; this river is situated in a very flat country, 

 ami makes an annual ileposit of a calcareous matter, which, liartlening, 

 raises the bed of the river in a sliglii degree every year. The ancient 

 inhabitants, to prevent their country from being inundateil, were ob- 

 liged to raise a small embankment on each side of the river— perhaps 

 two or three feet high — which, having served fur some years the de- 

 sired purpose, and llie bed of the river having become' higher from 

 the depi.^il, the einbankinenLs reipiired to have still more addi-d to 

 theni, until, after the lapse of centuries, tlic bed of the river, from the 



constant deposit of calcareous matter, and the consequent accessary 

 adilitions to the embankments, to the height of thirty feet, is now 

 several feet above the level of the surrounding country. This work 

 looks like one of our modern gigantic works, but it bears no compari- 

 son to the labours of the present day, it being but a work performed 

 from year to year, in small portions' at a time, while ours have been 

 formed at one operation. From all his researches, he, therefore, came 

 to this conclusion, that, until late years, eartliwork was but little known ; 

 he could make the same remark with respect to cutting. This work 

 was first treate<l systematically by military engineers in fortificitions 

 on the continent after the invention of cannon ; authors of that period 

 lay down many curious rules for forming ramparts. Various useful 

 calculations are given to determine the best mode of making the mat- 

 ter taken from the ditch exactly sullicieut to form the rampart, in order 

 that there should be none either to procure or carry away. The next 

 is in the construction of canals; the same rules were followed as in 

 the construction of ramparts. In road-making the same calculatioas 

 were made ; the whole aim of the engineer being to make the imagi- 

 nary line, called the "balancing line," so perfect, that the earth re- 

 moved from the eminences should fill up the hollows in the irregulari- 

 ties of the country through which the road was to be made. The 

 cause of these fine calculations was the difficulty and expense of carry- 

 ing away the superfluous earth to another place. The absence of 

 great undertakings on the continent is attributable to the want of our 

 modern appliances to get rid of the superabundant matter. In the 

 contracts sent in by foreigners for works abroad, it is amusing to see 

 the finical exactness with which the contractors calculate the expense 

 of removing the first 100 yards, then the next 25 yards, and so on in- 

 creasing until they get to 300 yards, beyond which the price is enor- 

 mous. It is only within the last three years that they seemed to have 

 the slightest idea of the plans in use in Eugland for facilitating this 

 work ; it is certainly not more than 30 years ago that we commenced 

 ufing the tramroad. First of all the' only plan was to remove the 

 earth in barrows, then the clumsy three-wheel cart was introduced, 

 after that tramroads, and now edge-rails, with the apjilication of a 

 locomotive, so that 30 years has changed the load from 2i cubic yards 

 to nearly 10 J. 



Before railroads came into general use, deep cuttings were executed, 

 and one remarkable instance Telford has left behind him in the Bir- 

 mingham Canal, which is remarkable for boldness of idea and success 

 of execution. Near Market Drayton there is an embankment, begun 

 15 or IG years ago, and which is as yet hardly finished, so great lias 

 been the slipping and so difficult the remedy. This work is a re- 

 markable instance of combined had eflects of a bad mixture ; the slopes 

 have flatted down until nearly in the proportion of 14 to 1, and it is 

 now more like a large hill than an embankment. There is an instance 

 of a deep cutting, by Dodd, at the Highgate Archway; it was in- 

 tended, first of all, to make a tunnel, but, from the constant slipping of 

 the earth, it was obliged to be made into an open cutting. The pre- 

 sent bold moile of cutting down large hills and filling up deep valleys, 

 in the formation of railways, is due to (ieorge Stephenson, ami in the 

 construction of large cuttings and embankments for canals to Telford, 

 whilst Dodd made the largest cuttings for roads. On the Holyheacl- 

 road the failure of the embankments and cuttings in the London clay 

 will teach a goud lesson to the young students. The point to Im> con- 

 sidered is, which, of m.isonry, ;iqueducts, tunnelling, embankments, or 

 cuttings, would be the cheapest nioile of doing the work proposed. 

 At the present time earthwork is the cheapest, for modern practice 

 has reduced it to a price per cubic yard. In the contracts for the 

 Paris and Kouen Railway, the contracts sent in by the French engineers 

 were invariably 3 or 1 times the amount of those sent in by English 

 contractors — thus, notwithstanding the expense of transporting the 

 workmen into France, the whole of that work is in the hamis of En- 

 glishmen. 



The engineer, to form a just calculation, must well study the charac- 

 ter and inechauical properties of the soil and the necessarv slopes. 

 Experience alone can teach these points. There are manv varieties 

 of the London clay, which, when cut dosMi to a certain depth, on ex- 



fiosure to the atmosphere are sure to slip; another cause is, the great 

 laste with which the embankments, Xc., are formed. When the water 

 does not penetrate, this clay is very h ird, but after exposure it melts 

 aw:iy, like tallow, anil the only remedy is to get riil of the water bv 

 rlrainiiig. When a slip tikes place, the toe of the embankment bulges 

 forward; in the first instance, the surface should 1m' well drained a 

 short distance from the edge the drain to Im" puddled, in order that 

 the water should nut penetrate ; borings should lie inaije liori/ontallv 

 anil the water tapped ; when expei.se ami time are no objects, the 

 whole should be cut in steps, ami ilraineil by means of w.iltles, so that, 

 if a slip takes place, it is only partial. The force with which the toe 

 of the embaiikinent bulges out is sucli that a wall of masonry would 



