1841.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL 



165 



's, I think, no doubt that placing solid dams at intervals across the stream, 

 whether directly or obliquely, and from five to e'even feet above the present 

 bottom of the river will diminish the velocity of thcit portion of the water 

 which is below the level of the weirs, and near them, and of the whole de- 

 scer.ciing column for a very considerable way up the liver ; and that in this 

 length so interfered with, particularly near tire weirs, first the water Hill be 

 kept back, then a deposit will take place, which will diminish the depth, and 

 therefore raise the surface of the water and increase the floods. Tlic bed of 

 the river will, in fact, be raised, unless kept down liy constant dredging. But, 

 even with dredging, the height of the surface of lire water will be raised, in- 

 dependenll} of the bottom. \Vhen Mr. Cubitt says, " there « ill be a greater 

 water-way on any cross-section at the weir after its erection than before," 

 he either refers to length only, or to some particular depth over the weir at 

 the time of some very extraordinary flood, because the sectional water-way 

 can only be measured from the top of the weir, all under that part being, by 

 the erection of the weir, taken from the area of the water-way. M'ithout, I 

 am sure the most remote intention, the position here stated is apt to mislead ; 

 and, independently of the above, I do not calculate on much good from the 

 obliquity of the dams, unless the river be enlarged for a great length above 

 them, so that tlie stream of the water may come at right .angles nearly to the 

 dam. Besides this, there can be no doubt that these permanent weirs will 

 increase the difliculty. to say the least of any great future improvement to 

 the drainage of the country above them. 1 do not mean to say that the 

 dredging and deepening of other parts of the river will not diminish theeff'ect 

 of the obstruction, but the dams are so much higher than the shoals to be 

 dredged, thai 1 do not think they will by any means counteract the injurious 

 effect, while the dredging without the solid dams would do as much good to 

 drainage as to navigation. 



Shropshire Nangatioii. — To the Shropshire navigation, also, from Ironbridge, 

 the solid dams would be a great obstruction. The statement is, that these 

 boats remain aground at IronLridge during droughts, and until there is a 

 fresh in the river, when they come down in lieets of twenty to thirty in num- 

 ber, making the passage of seventy miles to Gloucester in from eleven to si.\- 

 teen hours ; that there they unload their cargoes wilh the greatest dispatch, 

 th: t they may get up again before the water has gone down. 1 cannot see 

 how, to this description of trade very serious delay by solid weirs is to be 

 prevented, when each boat is to be locked down and up through five locks," 

 independently of the risk of being carried over the weir when the velocity is 

 considerable. 



Can, then, the present delay during droughts be remedied, and yet these 

 evils prevented? I think they can, even presuming dan>s to be necessary, 

 by forming them not as solid weirs, but as opening gates, to he shut in limes 

 of drought only, but to remain open to the bottom of the river in times of 

 flood, ami whensoever there is abundance of water for navigation, so that 

 both the flood waters and the trade may pass through the gates without in- 

 terruption or delay by lockage. These gates need not be the whole width of 

 the river, but the sides only, the space between the banks and the gates, 

 should be furnished with sluice or draw-doors, to open so as to pass the floods, 

 and to this tliere could not, as it appears to me, be any reasonable objection, 

 unless the expense be such as to e-^ceed the benefit, which when the importance 

 of the navigation is considered, would not. I apprehend, be the case : but if 

 it should be so. I still think that much good might be done by dredging the 

 shoals, and contracting the width, where the too great width is the cause of 

 the formation of the shoals, which, unless where the material is hard, will 

 probably be found to be the case. In most cases, as appears upon the sec- 

 tions, the material of the shoals is too hard to be acted upon by the floods, 

 and then the shoals, once dredged away, will not be likely to form again. 

 Should not the experiment be made ? it would be useful, even if dams were 

 constructed afterwards. Undoubtedly the floods of the Severn, if more con- 

 fined within their channel, would keep a large water-way open. 



Worcester to Gloucester. — What 1 have yet said as to dams is confined to 

 the part of the river above Worcester. Below that city the river assumes a 

 diflerent rharacter, the depth is greater, and the quantity of low land which 

 is liable to be flooded more extended. The entrance of the Birmingham and 

 M'orcester t'anal is below M'orcester : and I have been informed that two- 

 thirds of the tonnage that goes above Gloucester does not go higher than 

 Worcester. Hence, therefore, both as respects drainage and trade, an open 

 unobstructed river between Gloucester and Worcester becomes much more 

 important than above Worcester ; the expense of a dam also, such as I have 

 described, much greater, and I hope, and indeed think, it may be dispensed 

 with. Mr. Rhodes designed his ship lock and weir at Saxon's Lode, 17J miles 

 above Gloucester, or one mile below Upton Ham, wdiere Mr. Cubitt now pro- 

 poses it ; but, in consideration of interi^ring wilh the drainage of the district, 

 he was induced, in his subsequent plan, as 1 understood him to say, to remove 

 it uptoCleve's Lode, 23i miles above Gloucester, or 5 miles above Mr. Cubitt's 

 present site. Now, Worcester is only C miles above Cleve's Lode, or 11 miles 

 above Upton Ham. In this length there is more than six feet in depth, ex- 

 cepting at the shoals, which do not appear more numerous than lower down 

 the river, w here the depth is proposed to be obtained by dredging. The aver- 

 age fall in the river, from Upton Ham to ^Vorcester, being only 4i inches per 

 mile, 1 think there is little reason to apprehend a want of depth at the upper 

 end, after such a deepening and regulating as will be required. If the exca- 

 vated material were applied to raise the banks, the land would be less liable 

 to be flooded, and the scour being confined in the channel of the river, would 

 increase the depth. It will be understood that my objection as respects floods 

 is confined to tlie space above the first weir — all below the weir will be im- 

 proved by Mr. Cubitt's plan. 



Thus, also, the objection made, reasonably as I think, to the inadequacy of 

 one lock to pass the trade, would be obviated, as so large a proportion would 

 stop at Worcester, short ot the lirst lock. 



Clyde. — The Severn here is in some respects different from the Clyde, but 

 there is a similarity, and the good eSects of not adopting Smeaton's plan of 

 damming the river so as to secure a promised depth of 4 ft. H in. at Glasgow, 

 at high-water neap tides, even after an act had been obtained for it. but of 

 deepening and regulating, by which there is now 13 feet, has made that cit j- 



what it now is, and has much increased the value of the low lands, which 

 were more liable to be flooded than they now are. One would expect the 

 Worcester, of all parties concerned, to be least the advocates for dams and 

 locks between Gloucester, and their city, to limit the capability of their trade 

 in the size and number of vessels ; until, at least, it be proved that they can- 

 not be dispensed with ; and, whenever this is the case, the importance of 

 having the gates constnieted as I have described, to be shut in short-water 

 times only, is greater here, on account of the extent of flooded land, than 

 above ^\'orcester. Wiiether referring to the extent of the trade, to the delay 

 wliich will be consequent upon passing every thing through a lock, or to the 

 drainage of the country. I tliiuk solid weirs objectionable ; and if this be the 

 case now, it will be much more so after the river is improved, if an increase 

 of trade, with the introduction of steam-tugs, be the consequence, as is pro- 

 bable. A tug would take a whole fleet of boats or barges behind lier. The 

 Severn is at present far behind in the power applied to track the boats, being 

 partly horse and partly human labour ; and 1 decidedly think the solid weir 

 w ill tend to perpetuate the slow system. Until steam be general, the towing 

 paths ought to be raised and improved. They appear to lie in the hands of 

 two joint stock companies, and the bill does not attempt to interfere uitli 

 them, excepting at the proposed new cuts; but perhaps a great reform has 

 taken place in their condition since 1836. The lowing paths on the Clyde 

 are entirely abandoned, every thing being done by steam-boats or steam-tugs. 



Works above Worcester. — The dams above Worcester, as I propose them, 

 would be mere expensive than Mr. Cubitt's. I think it probable, supposing 

 dams to be indispensable, that a smaller number might sufl^ice, for the follow- 

 ing reasons . — The average present summer inclination in the surf.ace of the 

 river above Worcester is 21J inches per mi!e. Mr. Cubitt appears to suppose 

 that, after the construction of the weirs this will be reduced to little more 

 than one inch per mile, which I think very much under the mark, and there- 

 fore that the pen of the weirs will reach very much higher than he supposes, 

 thus allowing sufficient depth for a greater length between the locks, which will 

 be desirable. And here I may say, that I do not agree with Mr. Cubitt, w lien 

 he states that. " if all below tlie entrance of the Gloucester and Berkeley Canal 

 be left untouched, it is evident that no alteration will be made in the height 

 of the water up to the first weir." On the contrary, every obstruction or 

 shoal that is dredged in the whole length, tends to lower the water in the 

 part of the river above it. Tiie section ot the stream being increased by the 

 removal of the shoal, a less velocity, and therefore less slope in the surface 

 of the water, is required fr passing the descending water, and hence a sink- 

 ing of the surface increasing upwards. This must be compensated for by 

 greater dredging toward the upper end, to give the required depth. There 

 ought not to be a difterence of opinion on this point, and therefore either the 

 expression does not convey Mr. Cubitt's meaning, or I have misunderstood 

 it. * *■ * 



James Walker. 



23. Great George Street, Westmhister, 

 March, 1811. 



THE TOMB OF THE GREAT CAPTAIN. 



(From Dr. James Macauley Foreign Secretary of the Botanical Society, 

 Edinburgfi.J 



Of the many historical monuments which are met with in the ancient city 

 of Granada, one of the most interesting is the tomb of Gonsalvo of Cordova, 

 the Great Captain. This tomb would in any other place have been a cele- 

 brated point of classic pilgrimage ; but in a city containing the Alhambra and 

 so many glorious remains of the Moslem empire in Europe, other objects of 

 historic interest have been almost wholly overlooked by travellers. My at- 

 tention was called to it by a note in my copy of Don Quixote, where it is said 

 that " Gonsalvo toward the close of his life founded a monastery in the neigh- 

 bourhood of Granada, and was buried in its church. His epitaph, which still 

 remains there, is simple and grand; Gonsalvus Ferdinandus a Cordoba, 

 Dux Magnus Hispaniarum, Gallorum et Tdrcorum Terror." On 

 making inquiry, I found that the tomb was not in the mouasteiy he had 

 founded, whicli was that of Cartiija, but in the chapel of the convent of San 

 Gerouimo. Of tlus magnificent edifice, the Nuncio Aldobrandini, while con- 

 versing in the Alhambra with Philip V., said that " he had seen nothing in 

 Italy more great in architecture." Separating from this what may be due to 

 the'flatteiing courtesy of a foreigner, there is yet in the remark a good eulo- 

 gium of the work, and a high testimony to the merit of the architect, the 

 famous Diego de Siltie. He it was who also built the cathedral of Granada, 

 which in magnificence and taste exceeds all the cathedrals of Spain, and may 

 be ranked with the finest edifices in Europe. He spent thirty years in the 

 construction of the convent of San Geronimo ; a truly noble piece of archi- 

 tecture, whether we regard the grandeur of the design or the beauty of the 

 details, and a work worthy of the high name which Diego de Siloe bears in 

 the history of art in Spain. The place is at present used as a barrack for 

 soldiers. The remains of Gonsalvo are in a vault in front of the altar in the 

 chapel. This part of the building is in a most desolate and dismantled state, 

 every vestige of decor.ition and ornament baring been destroyed, and the very 

 woodwork of the chapel having been torn down for firewood, ^^'hat a con- 

 trast from the former condition of the place, when historians relate that the 

 shrine was famous for its riches and splendour, and the walls were covered 

 with trophies taken from the enemies of Spain, among which were two hun- 

 dred banners and two roval standards taken by the Great Captam ! The 



