1843.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



i:w 



ABERYSTWYTH HARBOUR. 



Sir — In perusing "Blackford and Imray's Charts and Sailing Di- 

 rections for St. George's Channel, 2nd ed." lately published, at p. 40 

 I find an account of this harbour as follows : — "Aberystwyth Harbour 

 is a narrow creek, and not fit for vessels that draw above 9 or 10 feet 

 water, and these must have spring tides to go over the liar." From 

 the following account it will be seen what alterations have taken place 

 through engineering skill, which has completely set aside the above 

 description. 



The Harbour of Aberystwyth is situated in the bottom of the Bay 

 of Cardigan, terminated by Bardsey Island on the North, and Strumble 

 Head on the South, and lies about 5 leagues E.N.E. from New Quay, 

 but more immediately between two points of land, the Castle Hill on 

 the North, and Alltwen on the South. Between these two points of 

 hind, the Rivers Rhydiol and Ystwyth empty themselves into the sea. 

 Aberystwyth Harbour may be distinguished at some leagues distance 

 by Pen Dinas Hill, which rises steep on the south end, also by the 

 ruinous castle near the town. 



The sea coast here about is nearly N.N.E. and S.S.W. by compass 

 bearings ; the prevalent winds from the W., and more especially from 

 the W.S.W. produce the heaviest swells; for in that direction the 

 Abervstwvth coast lies exposed to the fury of the Western Ocean. 



The Harbour, in its original state, was probably only the mouth of 

 a mountain river, the Rhydiol, which, after a course of about 20 miles 

 through a slate stone soil", falls into the sea. The Rhydiol, like other 

 mountain streams, is subject to sudden and violent floods, or freshes, 

 during rainy seasons, and a great quantity of slate, gravel, and other 

 matter is brought down the river by the effect of these freshes. The 

 foregoing observations equally apply to the River Ystwyth. The 

 "Sfstwytll having united its waters with the Rhydiol at the entrance of 

 the Harbour, these two rivers maintain one common outfall, through 

 the beach into the sea. The slate gravel brought down the rivers, 

 and the beach that was brought from the southward, accumulated, and 

 being thrown up by the action of the sea, a bank or bar was formed 

 at low water. This bar offered a constant obstruction to vessels, in 

 their ingress and egress, and often caused great destruction of life 

 and property. 



Now to show what engineering has done. In the year 1S38, the 

 trustees commenced a substantial new stone pier on the south side of 

 the entrance of the harbour, to protect the harbour from the western 

 gales, and to prevent the beach from accumulating and forming a bar. 

 This pier is now (1843) extended from the beach 2G0 yards in the 

 direction of SSE and NNW, and as far as i* completed, has fully an- 

 swered their expectation. In the first place, it has stopped the pro- 

 gress of the beach, and deposited the same at the back of the pier. 

 Secondly, it has guided the rivers into a proper channel, by which it 

 has caused a deeper channel to be formed, and removed the bar. 

 Thirdly, instead of 9 or 10 feet water at spring tides, it has now ob- 

 tained that height or more at the neap tides, and an average of 16 

 feet at spring tides. Lastly, it has removed that danger to vessels 

 and mariners arriving or sailing or having to wait in the bay during 

 the neap tides, for water to enter the harbour. The portion of the 

 river Rhydiol and the harbour at high water, occupy an area of about 

 20 acres. On the pier is erected a powerful capstan, supplied with 

 ropes, and a store house ; and about 400 yards to seaward off the end 

 of the pier, are moored two large transporting buoys, lying in 4i fa- 

 thoms low water spring tides, for vessels to moor to or warp from, 

 and every facility is rendered vessels making or leaving this port, by 

 signals and lights at tide times; it is now considered by all mariners 

 th,it visit this port to he the best tidal harbour in the principality, 

 when, but a few years sincp, it was the worst. 



Vessels visiting this port can be supplied with everv accommo- 

 dation for repairing, &c, there being two ship-building departments, 

 a rope walk, and sail makers, also bar and block warehouses. The 

 markets are well supplied, and sufficient stores can be obtained. 



An Old Subscriber. 



Aberystwyth, March 1st, 1843. 



STEAM POWER. 



Sir.— The detailed table of the values of the different degrees of 

 expansion in the engines of the Great Britain, which appeared iu the 

 March number of this Journal, afforded me much pleasure, since they 

 will tend to produce a conviction of the advantages in the minds of 

 owners of steam boats, who might disregard the form in which it has 

 been already advocated in your pages. 



In consequence of an inadvertent change, of my expressions from 

 " a. cubic foot of water expended us steam, is equivalent to one horse 

 power per hour," to " the evaporation of a cubic foot of water is equal 

 to one horse power," you appear to have overlooked the limits I 

 intended to apply to the assertion. The w«>rds in italics, which had 

 been used in a few lines above as " expended as steam in the cylinder" 

 were inserted to exclude the power due to expansive action, as well 

 as the waste, 1st, in blowing off, 2nd, at the safety valve, 3rd, clear- 

 ance steam, and 4th, cooling. I happened to roughlv estimate these 

 losses at 1 lb. of water for an expenditure of 7 lb. of water as " dense 

 steam" doing work in the cylinder, while the communication with the 

 boiler remained open, making the boiler evaporation identical with 

 your assumption; and I feel assured you will grant me permission to 

 refer to this charge of inaccuracy, and to the standard of h^rse power 

 assumed in my remarks on nominal horse power in the Nautical Ma- 

 gazine. 



I merely followed TredgoM in the assumption that steam of atmo- 

 spheric strength will produce 3,600,000 lb. pressure one foot high, and 

 consequently maintain dining one hour, a gross power on the piston of 

 60,000 lb. one foot high ; and I apprehend this assertion is equally tun-, 

 with a slight increase for higher steam, and a slight decrease for steam 

 below the atmosphere for the " dense steam" not worked expansively. 



As a secondary assertion I added " this gross power is capable of 

 producing 33,000 lb. on the connecting rod," and perhaps in the best 

 engines from 40 to 50 per cent, more, still it is not competent to pro- 

 duce an excess of 73 per cent., and much less an excess of cent, per 

 cent, as due to 14lb.net pressure, which amounts to O'J.OOO lb. per 

 minute. 



This standard of 00,000 Ih. gross pressure I had understood has 

 been occasionally used, or been recommended to be used, by civil 

 engineers in contracts, to prevent disputes with engine makers re- 

 specting the excess of power above nominal horse power to be sup- 

 plied, and it seems a fair mean. Moreover, it meets the difficulties 

 arising from higher steam, and the reduction of power due to expan- 

 sion, and it is equally applicable to non-condensing engines ("the esti- 

 mate of horse power of these engines seems somewhat undefined). 



The employment of an indicator, the value of which you have ad- 

 verted to, is obviously required in estimates of the above nature ; and 

 though well adapted as a standard of comparative power and coal 

 consumption, yet nominal horse power might still be used as a mea- 

 sure of the size of the engine : which seems a good commercial unit, 

 of the same value as the diameter in inches, of the cylinder used in 

 Cornwall, where the loads vary from 51b. to 161b. per square inch, 

 and the strokes from 2 to 11 per minute in large engines. 



Accustomed to refer to the "work performed " or duty, I concur 

 entirely in the appeal to the " wotk to be done" by the engines of the 

 Great Britain, especially as I anticipate the most favourable results 

 from the mode in which the designers of the Great Britain have 

 availed themselves of the condition that their capacities increase iu 

 a faster ratio than the areas of the midship sections of vessels. 



I have the honour to remain, Sir, 



March 10th. Your's, obediently, 



John S. Enys. 



INSTITUTION OF CIVIL ENGINEERS. 



Jan. 10. — The Pcekident in the Chair. 



The business of the meeting was commenced by reading an abstract of 

 Mr. Davison's paper (No. 539) describing the mode adopted for sinking a 

 well at Messrs. Truman, Hanbury, Buxton, and Co.'s Brewery, which was 

 published in the minutes of proceedings of session 1842, p. 192, and the fol- 

 lowing observations were made. 



Mr. Braithwaite described the difference between the method employed in 

 sinking the well for Messrs. Truman and Co., and that for Messrs. lieid and 

 Co. In the former the bore was small, and would therefore only produce as 

 much water as was procured from the veins through which it passed ver- 

 tically, while the latter, by its larger diameter, permitted lateral galleries to 

 be dnveu in the direction of the fissures in the chalk : thus forming feeders 

 for the well, and at the same time capacious reservoirs wherein the water 

 accumulated when the pumps were not a; v. oil,. 



He attributed the comparative failure at Messrs. Truman's to errors in the 

 mode of sinking: the length of the cylinders which had been attempted 

 to be forced down was too great, and the lateral pressure had prevented 

 them from reaching the chalk, so that when the pumps were set to woi k an 

 undue quantity of sand was drawn up with the water, causing a cavity be- 

 hind the brick-work, which at length fell in. The water having been 

 pumped out to a lower level than was proper, the equilibrium between the 

 water and the sand around the cylinder had been disturbed, and the "blow" 

 of sand had ensued. 



The New Kivcr Company had been advised to sink a well of sufficient 



