Document 35 P 17
| 72 | ||||
| double pumps and two single ones they had not been able to sink the | ||||
| Surface of the water within the Case above an inch below the Surface on the | ||||
| Outside- In this Method however the Coffer dam Cases used at Perth | ||||
| Bridge were driven so as to keep the water out of the foundation Pitts | ||||
| when the surface of the River (when the Tide was in) was from six to seven | ||||
| feet deep upon the Bed of the River and Consequently against the sides of | ||||
| the Casing it would therefore have seemed that there had been some very | ||||
| palpable defect in driving these Cases had not the operations of the second | ||||
| Pier from the North side sufficiently shown how extremely open this Bed | ||||
| of Gravel is to the passage of water and how impracticable every method | ||||
| was likely to prove that depended upon the drainage of the water from | ||||
| the Piers to be placed in the Main Channel of the River. | ||||
| Several very rapid and much larger Floods than that which did | ||||
| the Mischief happened in the course of the succeeding winter particularly | ||||
| one upon the twelfth of December when the water was within nine inches | ||||
| of the top of the impost when Mr Pickernell marked a fall of two feet three | ||||
| inches but without any material damage to anything which naturally | ||||
| induced all those concerned to proceed in the way they were then going on. | ||||
| The season of One thousand Seven hundred and Seventy nine was | ||||
| begun by new founding the western half of the Pier that the weather pre- | ||||
| -vented from being completed the year before which was the fifth from the | ||||
| North and was done without Caisson or draining the water by means of an | ||||
| Air Chest or diving Machine that had been very successfully and Conveni- | ||||
| -ently employed in undersetting the other three damaged Piers and the | ||||
| Pier before unbegun (being the Sixth from the North was the next in Course | ||||
| founded by Caisson but with this difference that the Case was first drove | ||||
| all except the down stream Salient Pointing before the Caisson was floated | ||||
| into its place through this opening. | ||||
| It would cause too great a prolixity to describe the particular | ||||
| 17 operations | ||||
Note: Mr Smeaton's Memorial, p 17
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| An entry outlined like this has a note which may be seen by hovering over it. |
Transcribed by CTW and KS