234 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



causing the pump-pisfon to descend is so much loss, because it has no 

 useful eft'ect in drawing the train-piston forwartt. We make the re- 

 mark because it miglit otherwise be made a point of argument tliat the 

 atmospheric pressure assists the piston'sdescent as much as it impeded 

 its ascent. Tlie case is exactly anahigous to that of a man Aa«//wg' 

 up a weight by a rope. When he has raised the weight a certain 

 distance, he takes a lower part of the rope in his hand, and again 

 raises the weight a certain distance, and so on. But it is c-rtain that 

 the alternate action of dcpressinghis hands has no direct usefcd effect: 

 the whole amount of available force is that exerted in raising his 

 hands. 



Now then for fig. 2. Here, as our correspondent observes, if the 

 pressure in the main pipe be 5 lb. to the incli, the pressure on b will 

 not be equal to the full atmospheric pressure till 'inU of llie upward 

 stroke have been accomplished. It will therefore be only through 

 one-iliird of the stroke that the retarding force on the pump-piston is 

 15 — 5 lb., whereas that force is exerted on the Irain-jjiston through a 

 distance equal to i\\e whole stoke: for the remaining two-thiids the 

 retarding pressure on the puinp-pislon varies acccrding to its height: 

 when it is at the bottom of the cylinder the retarding force is 0, when 

 frds of the way up, lOlb. Thus tlierefure by the contrivance of a 

 cap and valve in the top of the cylinder a saving is effected in the 

 upward stroke. But it is all lost again in the downward stroke. For 

 whatever pressure is by ihiscontrivance removed from Iheuppersurface 

 of the su'ker in the upward stroke, the s.une is a so lost in the down- 

 ward stroke. And as that downward stroke, although it do contribute 

 nothing to the progress of the train, has to be made, it is obviously no 

 economy of power, to diminish the resisting force on the piston up- 

 mards to the same extent that we lose the accelerating force on it 

 downwards. 



It seems, then, that with either kind of pump the force lost is in 

 effect the same ; assuming alioays \\\,il the statical |iressure of air is 

 sufiposed to operate. But as this is obviously not true (in all proba- 

 bility not even approximately true), it were much to be preferred that 

 the statement of power wasted should be expressed as in the paper 

 undfr discussion — namely, as terms of strokes of the engine. In this 

 way, all difficulty as to the nnknuwu properties of air in motion is 

 avoided, and we think our correspondent will allow that for any kind 

 of |jump the nunibtr of strokes wasted is as staled in the paper. In- 

 deed the waste is there underrated, for the return strokes of the air 

 pumps are clearly so much loss. This consideration certainly ought 

 not to have been omitted in the paper, that while the train is moving 

 the number of strokes is twice as manv as they ought to be, because 

 for every foot the train piston advances the pump piston advances a?iii 

 returns the same distance. 



The strictures on the paper on the Artizan Club's Treatise we 

 cannot so satisf.ictorily answer, simply because we do not comprehend 

 them. In saying this, we are using no editorial figure of speech, but 

 stating the plain truth, that we cannot find out the meaning of our cor- 

 respondent. However, to deal by him fairly, we must give his own 

 words. After asserting that the paper is full of blunders, he pro- 

 ceeds — 



Many of them have arisen from " H. C." having got the idea of steam and 

 steam engines so conglomerated in his brain tliat he cannot separate them, 

 and when the Club is talking learnedly on steam " H. C.'s" ideas are running 

 riot among steam engines. You may increase the mechanical effect of a cer- 

 tain weight of steam by the very same operation that diminishes the power 

 of the engine. In the Cornish engine, tlie sooner the steam is cut olf the 

 greater is the effect produced by a cubic foot of water as steam, but the less 

 is the power of the engine. 



On the last dozen lines of the paper he observes — 



Mark how adroitly the power of the engine is here ascertained from a for- 

 mula for the power of steam. 



We do not know what private interpretation our correspondent 

 gives to the term " mechanical effect of steam," but surely he must 

 allow that if the Artiz in Club assert that an infinitely great mechanical 

 effect can be produced with no steam, they utter an iiDsurdity ; that if 

 they assert that the friction of the piston depends on the temperature 

 of the steam which has acted upon it sometime previously, thev utter 

 an absurdity; if they say that the powerof an engine is always exactly 

 doubled by using a condenser, they utter an absurdity ; and if tliey say 

 that the amount of a force is dependent on the work it has to do, they 

 utter an absurdity. Will our correspondent undertake to say tli.it 

 these blunders cease to be blunders by giving a particular meaning to 

 the phrase "mechanical effect?" Will he deny that such errors would 

 be disgraceful in a common mechanic, and are absolutelv revolting in 

 those who underiake to teach, armed with all the authority of malhe- 

 malical symbols ? 



The last argument of our correspondent is, that many of the Artizan 



Club's theories are taken from Trcdgold. This makes the matter no 

 better. We are amongst those who think that it is not a necessary 

 consequence that, because a theory comes from Tredgold, it is there- 

 fore true. His own editor, Woolhouse,lias been compelled to correct 

 mathematical errors for which a schoolboy would be punished. We 

 allude now, more especially, to the investigations connected with 

 rotary engines. The position, then, in which our correspondent puts 

 the treatise of the Artizan Club is this, — that it is not only an erroneous 

 but a dishonest production, for the matter is taken from Tredgold 

 without the slightest acknowledgment. Our correspondent, how- 

 ever — to do him justice — reprobates the plagiarism as warmly (or more 

 warmly) than we ourselves should have done. To conclude — he is 

 clearly one who thinks, though sometimes, he will furgive us for say- 

 ing, he thinks hastily. It is a hard matter to attain the truth in phy- 

 sical investigations; but we put ourselves absolutely beyond the pale 

 of philosophy by forming intemperate and undigested conclusions. 



ACCOUNT OF IMPROVEMENT OF THE NAVIGATION OF 

 THE RIVER CLYDE. 



(With an Engraving, Plate XIX. ) 

 (From a Memoir addressed to M. Arago, fur the Royal Institute of 

 France, by W. Bald, Esq., C.E., Ftdoro of the Royal Society of 

 Edinburgh, and the Geological Society, London, Sfc, 4'<^-) 

 As the improvement of the navigation of the river Clyde has been 

 one of the most successful engineering operations achieved in Great 

 Britain, a firw short observations regarding this subject may be inte- 

 resting. The river Clyde may be said to have been the cradle of 

 steam navigation in Europe, and on the banks of that river was bora 

 the illustrious Watt. 



The following is a list of the various reports which have been made 

 regarding the improvement of the navigation of the river Clyde. 



In 1755 Mr. John Smeaton, civil engineer, made a report upon the im- 

 provement of the river Clyde, and he recommended that there should be a 

 lock and a dam across the Clyde at Marliuford, but which was never exe- 

 cuted. At that period vessels dra-ving 3 feet 3 inches to 3 feet C inches of 

 water could only ascend the Clyde to the harbour of Glasgow. 



In 1768 Mr. John Golborne, civil engineer, made a report upon the im. 

 provement of the river Clyde. lie recommended that a series of jetties 

 should be constructed on the right and left banks of the river, so as to nar- 

 row the Clyde, fix the channel of the navigation, and Increase the scouring 

 power of the river; he also recommended the removal of several shoals or 

 banks lying in the channel of the river. These works were carried into exe- 

 cution, and did considerably improve the navigation. 



In 1769 Mr. James Watt, whose name has been so illustriously connected 

 with the steam engine, made out a short report upon the Clyde : it refers to 

 levels and depths of water only. 



In 1781 Mr. John Golborne again reported on the river Clyde, and the 

 works of the jetties, &c. 



In 1799 Mr. John Rennie, of London, reported upon the improvement of 

 the Clyde. He recommended longitudinal dykes, and that the jetties should 

 be shortened in several places. 



In 1806 Mr. Thomas Telford reported upon the irriprovement of the Clyde. 

 At this period vessels drawing 8 feet 6 inches of water could ascend the 

 Clyde to the harbour of Glasgow. 



January 26, 1807. Mr. Rennie reported upon the Clyde. He recom- 

 mended wet docks. 



June 15, 1807. Mr. Rennie again reported. 



Dec. 24, 1807. Ditto. 



Dec. 26, 1807. Ditto. 

 1809. Ditto. 



Dec. 29, 1819. Mr. Telford reported on a wet dock. 



Dec. 20, 1821. Ditto. 



1824. Mr. Whidbey reported upon the improvement of the 



River Clyde. 

 1826. Mr. Telford reported. 



1834. Mr. J. Hartley reported. 



1835. Mr. Logan reported. 



1836. Mr. Walker reported. 



1838. Mr. John Scott Russel reported. 



1839. Mr. Bald reported. 

 1841. Ditto. 



1843. Ditto. 



Within the last six years the following impediments to the free 

 navigation of the river Clyde have been removed, by cutting channels 

 through the Port Glasgow bank, the Garinoyle bank, the bank oppo- 

 site to Dunib.irton Castle, the bank at the head of the Long Dyke, and 

 also through all the hard ground shoals, consequently the channel of 

 the navigation has been considerably deepened, so that vessels now 



