1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



BALLARD'S ICE BOAT. 



79 



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The above engraving is an isometrical view, drawn to a scale of 

 eight feet to the inch, of the ice boat, for which Mr. S. Ballard, had 

 the honour of receiving of the Institution of Civil Engineers a Telford 

 medal. 



This boat was first used in the year 183", on the Hereford and 

 Gloucester Canal, and has been in operation, whenever required, ever 

 since. It breaks the ice by ploughing or forcing it upwards, and does 

 not require more than one-fourth of the power necessary to break the 

 ice on the old plan of forcing it downwards against the water. 



The ice-breaking frame A consists of three pieces of timber marked 

 n, fastened together by two cross pieces c and e. That part of the 

 frame which lies over the boat is boarded or planked over; one part 

 so as to form a platform for men to stand upon, the other part raised 

 in the middle and cased with sheet iron, that the ice may not lodge 

 on it. The frame lies on the front of the boat, which is sloped down 

 as shown at a b. The frame is made with deal timber; the two out- 

 side pieces each 27 ft. G inches long by 9 in. by Si in. the middle 

 timber 31 ft. long by 12 in. by 7 in. These timbers are rounded on 

 the top as far as they project over the front of the boat, and the uDder 

 sides are made narrower than the top sides. 



The boat is decked over from a to b, and when the ice is very 

 strong, she has a temporary boarding over, of inch board, as far as the 

 centre. The spar B, which projects over the stern of the boat, has 

 the large end chained down to the middle of the boat. 



The piece of timber C is attached to the spar B by a chain. It is 

 about one ton in weight, and prevents the boat rising behind when the 

 ice presses upon the frame on the front of the boat. It floats on the 

 water and the chain is strained in proportion to the thickness of the 

 ice. The timber is also chained to the stem of the boat. By these means 

 the slope or inclination of the ice-breaking frame is kept always the 

 same, with the advantage of a short boat, which is easily steered and 

 managed. 



The pole or shaft h is for the purpose of steering the boat. It is 

 attached to the end of the spar by a chain, and is balanced by a weight 

 n, so that its weight may be trifling in the hands of the steerer who 

 walks on the towing-path. 



The boat, and also the upper sides of the ice-breaking frame are 

 cased with sheet iron. The hauling line is attached to the chain o. 



When the ice-breaking apparatus is not required, it may be taken 

 off, and the boat used for other purposes. 



THE GREAT BRITAIN STEAM SHIP. 



It was but lately that our attention was drawn to an article, pub- 

 lished in the Xautical Magazine for January last, written by Mr. J. 

 S. Enys, entitled " Remarks on Nominal Horse-power," and which is 

 evidently a critique on an article of ours published in the Journal, 

 Vol. V. p. 357, on "The Great Britain Steam Ship," the same having 

 been copied into the Nautical Magazine of last November. 



The object of Mr. Enys's paper is to shew the fallacy of calculations 

 made on nominal horse-power, in fact power calculated by the rules of 

 the late Mr. Watt, in as much as modem practice has deviated from our 

 great master in the amount of boiler pressures, from 2 £ and 31b., to 

 5, 6, 7, S, and sometimes 10 lb. per square inch, and then proceeds to 

 prove that the consumption of fuel by the Great Britain will be just 

 one-half or one-third (according to the expansion) of that computed 

 by ourselves. — He states much that is true, and something that is 

 erroneous, and we consider, that he is guilty of omission; inasmuch, that 

 he does not follow out his argument (he is undoubtedly able) and de- 

 monstrate what diminution of speed would result on the employment 

 of expansion, especially to so great an extent as one-half and two- 

 thirds of the stroke. 



We must do ourselves the justice to say, and we are sure our 

 readers will agree with us, that our observations were temperate, 

 written, not in a feeling of opposition, but merely to elucidate and 

 draw attention to what we considered errors in practice. How far we 

 are correct in our views with reference to the case of the Great 

 Britain (late Mammoth) time and experience only will show, we are 

 fully content to abide by the issue. 



It will be seen on reference, that we expressly guarded ourselves 

 against any misunderstanding with respect to the character of our 

 data, and took the trouble to explain that we were indebted for them to 

 Mr. Hill, a writer in the 9%th Number of the Mechanics' JWagazine, so 

 that our deductions are dependent on the accuracy of the matter there 

 given. It does not, however, appear that Mr. Enys disputes any 



portion excepting the correct delineation of the boiler details, so that 

 we were right in taking the cylinder at 83 inches diameter, 6 feet 

 stroke, and 19 strokes per minute. In our article we entered 

 into a calculation, founded on the capacity of the cylinders and length 

 of stroke (commonly called nominal horse-power, the only data at 

 that time at our disposal), to prove that the consumption of . n.ils, 

 would, during a passage from Bristol to New York, be much greater 

 than is supposed, or than they have allowed space for in the vesseF. 

 We are met by the scientific calculations of Mr. Enys, proving that by 

 expansion to one half, or two-thirds of the stroke, the consumption of 

 coal would be considerably reduced, in a much larger ratio than the 

 power. It is, however, worthy of remark, that, although ourselves 

 and Mr. Enys take different methods of computing power, that we 

 agree in the amount of fuel which would be expended, supposing the 

 engines to work to their full power, namely 129 to 130 tons per diem. 



We have again carefully looked through Mr. Hill's paper, which 

 confirms our impression that he did not state any distinct rati oj t.c- 

 pansion at which the engines were to be worked, he explains the 

 construction of the expansion valves, which are not new ; and as most 

 modern engines of large powers are fitted with similar contrivances, 

 we concluded that in this, as in other cases, the evaporative power of 

 the boilers and strength of the materials were calculated to supply 

 steam for, and to resist the action of, the full powers of the cylin lers, 

 expanding the steam only by the common sliding valve, though 

 ments of the special expanding valves being nservedas in other ships, 

 for the occurrence of fine matter and/air winds. 



Our justification on this head will be eomplete, when we state, that 

 "The Great Western," Cunard's vessels, the "British Queen" and 

 " President," were each fitted with separate expanding ap] 

 but that their boilers are capable of generating a full supply of steam 

 for an expansion of not more than -£,th of the stroke— that is by the 

 sliding valve, and it would be a matter of curious enquiry to see how 

 frequently this is departed from. If our views be correct on this 

 point, the general object of commanders of steam vessels, is to make 



11 



