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has rarely been accomplished. A peculiar feature of these communications, and one to which the council would particularly advert, is, that they are not of a speculative character, but present a detailed analysis of authenticated facts. This analysis consists in separating and ascertaining the various results, and in referring them to particular classes, so that they may be readily appli cable in practice. The merit of instituting and recording a series of obser vations upon a scientific subject is universally acknowledged, but the reduc tion of such observations so as to form a standard of reference to which the practical engineer may appeal, is a task of far greater difficulty, and its exe cution of far higher merit. It is in this eminent rank that the council would place these communications of Mr. Parkes. The description by Mr. Leslie of the Harbour and Docks of Dundee, was also briefly adverted to in the last annual report, as one of those communi cations on which the Institution sets great value. It consists of a detailed account of the progress of the improvements projected by Smeaton, Telford, and others, in part carried into execution by the projectors, and completed under the author’s own superintendence since 1832. The illustrations of the projected and executed improvements with the plans, elevations, sections, and details of the works of the docks, gates, quays, cranes, and machinery employed, occupy 30 sheets of drawings. To the copious history and de scription of these works is added an extensive series of observations on the tides. The determination of these facts for different parts of the globe, is a question of the greatest importance in physical astronomy, and the council would take this opportunity of pointing out the essential service which may thus be rendered by the engineer to the cause of science by his lecording the observations which he has pre-eminently the opportunity of making. For this valuable record of an executed work, the council have awarded a silver medal, and a copy of the life and works of Telford. A silver medal and the life and works of Telford have been awarded to your associate, Robert Mallet, for his communication on the “ Corrosion of Cast and Wrought Iron in Water.” This communication presents features of no ordinary interest to the engineer. The comparatively recent intro duction of cast iron for the purpose of piling, for wharfs, &c., and of wrought iron in the construction of vessels, has rendered the subject of the action of water upon iron of peculiar importance; the British Association have, from time to time, granted sums of money for making experiments on this subject, and Mr. Mallet having been engaged in conducting these experiments, has selected from the very extensive series of results obtained by him, those con clusions which may be of service to the practical engineer. The most valu able portion of this communication consists of elaborate tables, which exhibit the results of the action of clear and foul sea and fresh water at different temperatures upon cast and wrought iron. Such being the general nature of the experiments, the results to which they lead, or the effects produced, present several remarkable characteristics, and it is found that the corrosive action of water and air combined, produces, on the surface of cast or wrought iron, a state of rust possessing one of five distinctive features, viz. uniform— uniform with plumbago—local—local pitted—tubercular: or some two or more of these in partial combination. The practical results which may be deduced from these tables are of the highest value to the engineer, and point to considerations of the greatest importance; thus the upper and lower strata of water, of different degrees of saltness and density, coming in contact with the same mass of iron, a voltaic pile of one solid and two fluid elements is formed, and under such circumstances the corrosive action is materially aug mented ; hence it follows as a practical conclusion, that the lower part of all castings used in such situations, should be of increased dimensions. Similar results, the knowledge of which is of great importance to the practical engi neer, such as the rapid decay of iron in the sewage of large cities, of the bolts of marine engines exposed to the bilge water, and of boilers containing hot sea water, are referred to actions due to similar physical principles. The protection which metals receive from paint, or from the presence of various alloys, so as to obtain a mode of electro-chemical protection, such that, while the metal iron shall be preserved, the protector shall not be acted upon, is aho referred to similar principles. The council have also awarded a bronze medal and books to Mr. Charles Bourns, for his communication on “ setting out railway curves; ” to Mr. Chapman, for his description and drawings of “ a machine for describing the profile of a road,” and to Mr. Henry Renton, for his description and drawing of “ a self-acting Waste-board on the River Ouse.” The communication by Mr. Bourns is an application of simple geometry, leading to practical results. In setting out curves recourse has been had to various expedients, but Mr. Bourns, in the propositions contained in this paper, has shown that, by the use of the common chain, an offset staff, and table of offsets, he is enabled to set out curves of any radius and flexure, with a facility and precision not generally attained. The description and drawings of a machine for describing the profile of a road, is one of several communications on this subject, sent in accordance with the notice of subjects for competition issued by the council. Many of the arrangements proposed by the author exhibit considerable ingenuity, and though difficulties may exist in their practical application, the council think thi6 attempt may be of assistance to others, who may have their attention directed to the construction of an instrument for similar purposes. The description and drawing of the self-acting waste-board on the river Ouse, being an account of an executed work, is one of those communications which the council are most anxious to encourage by every means in their power. The drawing and description furnished by Mr. Renton are highly creditable to the talents of the author, and deserving of some special mark of approbation. The council have also awarded books to the value of five guineas to £u- genius Birch, for his drawing and description of the machine for sewing fiat ropes, in use at Huddart’s rope manufactory. The rope machinery of Cap tain Huddart was, some time since, one of the subjects on which the council solicited communications; on that occasion two valuable sets of drawings were communicated, the one by Mr. Dempsey, the other by Mr. Birch. The subject of the present communication was not included in either of the pre ceding, but Mr. Birch, desirous of availing himself to the fullest extent of the liberality of Mr. Cotton, the then proprietor of the machinery, and of carrying out the views of the council, has devoted much time and labour to placing in the Institution, an exact record of everything connected with this interesting machinery. Premiums of hooks have also been awarded to Mr. Maude, for his “ Ac count of the Repairs and Alterations made in the construction of the Menai Bridge, rendered necessary by the gale of January 7, 1839,” and to Mr. Andrew Burn, for his drawings of a “ Proposed Suspension Bridge over the Haslar Lake.” The council would point out these instances of the fulfilment of the engagements entered into on election, to the attention of the other graduates of the Institution, who have similar opportunities, but who have not hitherto kept their promises. It is the desire of the council to obtain an exact record of works that are projected or in progress, and such records are peculiarly adapted to compete for the Telford premiums; Mr. Maude and Mr. Burn, with proper permission, have availed themselves of the facilities afforded them, and the council trust that the premiums now awarded, and the marks of approbation here expressed, will stimulate others to avail them selves of like opportunities. The authors of such communications will thus most materially contribute towards promoting the interests of the Institution, and to their own qualification for future employment and advancement in the profession. The Institution has received during the past year, many other communi cations of acknowledged merit, of which no mention has yet been made. To a few of them the council would now briefly advert, and especially to the last paper by Mr. Parkes, “ On the action of Steam in the Cornish Single Pumping Engine,” a communication of no ordinary importance and interest, either on account of its own intrinsic merits, as viewed in connexion with the past proceedings of this Institution, or the future pospccts of this depart ment of practical science. This communication, though intimately connected with those of the same author previously alluded to, growing immediately out of them, and depending upon the facts contained in them, is of a totally distinct character; being an attempt to explain, on theoretical principles, the action of the steam on the piston, and to unfold the real causes of the economy of the Cornish engines. This subject has occupied the attention of the Institution during the last four years, and the discussion first assumed a settled form during the session of 1837, on the receipt of the communi cation of Mr. George Holworthy Palmer, “ On the application of Steam as a moving power, especially with reference to the reported duties of the Cornish and ether Engines.” In that paper the author, reasoning on certain data as to evaporation, and on the physical facts which involved the con stancy of the sum of the latent and sensible heat in steam of ail elasticities, and of the absorption of heat by matter on dilatation, came to the conclusion that no power could be gained by expansive working, and that, consequently, this could not be the cause of the economy in Cornish engines. This dis cussion was revived in the ensuing session by the communications of Mr. Wicksteed and Mr. Henwood, the former furnishing the first recorded expe riment in which the water raised was actually weighed, the latter giving an extended series of most careful and detailed observations on the quantity of steam employed, the mode of its distribution, the duty performed by a given quantity of fuel, and the measurement of the water raised. Taking for data the facts furnished by Mr. Henwood for the Wheal Towan, and by Mr. West for the Fowey Consols Engines, Mr. Parkes has analyzed the quantity of action obtainable from the quantity of water as steam con sumed, and expanded to the extent used in those engines, and has found the steam’s force unequal to the resistance overcome. After satisfying himself from various phenomena attendant on the working of these engines, that the amount of resistance opposed 10 the steam was not overrated, he was led to conclude that from the instantaneous and free communication effected be tween the cylinder and boiler of these engines, by the sudden opening of the large steam valves, a force must be transmitted to the piston, of a kind dis tinct from that of the steam’s simple elasticity. This force he denominates the steam’s percussive action ; he adduces various proofs that this description of force has operated on the piston, and that it alone was equivalent, iu the instance of the Fowey Consols Engine, to drive the piston through -^^ths of its stroke. The author considers the effect produced on the piston of a Cornish En gine, by the sudden impact of highly elastic steam, to he similar to that ob tained from water in the hydraulic ram. He has not in his paper entered on the consideration of the absolute amount of percussive force, which can be afforded by an aeriform fluid in motion—but has confined himself to the de termination of the quantity of action, which he conceives to have been de rived from that source in the particular engines examined. He invites the co-operation of others in instituting experiments on this subject, and the Council hope that the ensuing Session will augment the number of facts re-