Jr Professor Faraday said that the Bude light, as proposed to the Trinity House, was an oil lamp, supplied with oxygen by an apparatus for generating it. In lighthouses, it was ing dispensable that the lamps should be so ar ranged that the lights should consume only a given quantity of oil, and retain an un varying degree of brightness for a given time, which was now four hours, at the end of which time they were trimmed. It was found that with the Bude light, the quantity of oil consumed was greater, and the lamps required trimming in two hours, in consequence of the wicks charring; these circumstances rendered the system inapplicable to lighthouses. Subsequently, five of the Budelight lamps had been referred to him by the House of Commons for experimental purposes, and his observations upon them were of the same nature.

Mr. Bethell explained, that in Mr. Gurney's s present "Atmospheric Gas-burner," the supply of oxygen alluded to by Professor Faraday was not used.

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Mr. Snow Harris inquired whether the action of carbonic acid, to which the term "poisonous" had been applied, was to be considered as positive or negative. How was it to be viewed in its connexion with the cir culation of the blood and with the process of respiration?

Professor Faraday replied, by quoting from the work of Dr. Marshall Hall,* that "It was first distinctly stated by Sir Humphrey Davy, that in inspiration, and during the pulmonic circulation, the double function was performed of 1st, the absorption of oxygen, and 2nd, the exhalation of carbonic acid, by and from the circulating blood, a doctrine from which another doctrine flows, viz., that, during the systematic circulation, the oxygen absorbed is continually undergoing the transition into carbonic acid." The general conclusion from his experiments was,

That respiration was a chemical process, the combination of phosoxygen (oxygen) with the venous blood, and the liberation of carbonic acid and aqueous gas from it."'+

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The Gulstonian Lectures for 1842," pp. 8, 12, Mr. Edwards, in his work, "De l'influence des Agens Physiques sur la Vie," 1824, p. 465, observes, "L'oxigène qui disparait dans la respiration de l'air atmosphérique est absorbé en entier. Il est ensuite porté en toute ou en partie, dans le torrent de la circulation. 11 estremplacé par une quantité plus ou moins semblable d'acide carbonique exhalé, qui provient en tout ou en partie, de celui qui est contenue dans la masse du sang. En outre, l'animal respirant de l'air atmosphérique, absorbe de l'azote; ćet azote est porté en tout ou en partie, dans la masse du sang. L'azote absorbé, est remplacé par une quantité plus ou moins équivalente d'azote exhale, qui provient en tout ou en partie du sang.

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Professor Graham, in a note to Dr. Hall, says, If an animal were to breathe atmospheric air to which carbonic acid were added, in proportion to this addition, the evolution of carbonic acid from the blood would, in my opinion, be impeded; the passage of the carbonic acid outward at all, from the blood, depending upon the comparative absence of that gas from the air taken into the lungs."

In treating of "asphyxia," Dr. Hall says, "The absorption of oxygen, or the evolution of carbonic acid, or both, are impeded or interrupted in every case of asphyxia. From the want of oxygen the blood is deficient in stimulus; by the presence of carbonic acid it is positively poisonous.'

It appeared from the researches of physiologists, that the presence of a certain proportion of carbonic acid was necessary to stimulate the action of the heart, and regulate the circulation of the blood; that nature kept up the proper supply for this purpose, but that any excess was prejudicial.

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Acting upon this principle, Dr. Payerne had brought forward a proposition for purifying the air in a diving-bell, so that without using the air-pump the diver might remain under water for four hours, or even longer. This was, the professor believed, accomplished by decomposing the carbonic acid, absorbing the carbon, and eliminating the oxygen, and not by generating oxygen, as had been generally imagined.

"On the construction of Valves used in Pumps for raising Water." By Samuel Collett Homersham, Assoc. Inst. C. E. The author first describes the original leather flap valves which are in common use, shows their defects, the modifications which have been introduced in them, and the reasons why a better kind of valye was necessary, particularly for large pumps appended to steam-engines, quoting from Mr. Wicksteed's work on the Cornish engine,* that by the closing of the valves at the East London Water-works, the whole of the engine-house was shaken. This led to the application, by Messrs. Harvey and West, of a modification of the double-beat steam valve, only making it self-acting; by this, it is stated, the concussion is so much re"duced that little inconvenience is felt from -patto vid tudi fotoja muka

.it. No air is required to be admitted beneath, as is frequently the case with common valves, consequently the pump, when at work, lifts its full complement of water.

The author states that in this valve the diameter of the top-seating is somewhat smaller than the lower, for the purpose of allowing a sufficient area for the pressure of the water to act against in lifting it. He remarks that the pressure required to open these valves appears to vary from 2 lbs. to 5 lbs. per square inch, and that it does not seem to follow any uniform rule. The seatings which answer best are composed of pieces of wood fitted in a groove with the fibres in a vertical position. The principal advantages of this kind of valve, as to durability, slight concussion on closing, facility of repair, &c., are then enumerated; but it is urged against them that the passage for the water is circuitous, and therefore the power required to force the water through is considerable, and that in a large valve the height to which it rises is too great.

He then states that Mr. James Simpson, who has had great experience in the difficulties attendant upon the use of large pumps, some years since conceived the idea of obtaining valve openings nearly equal to the full area of the clack chambers, by means of a conical valve formed of rings shutting down upon each other; this was afterwards modified into a valve with separate seatings for the rings to fall upon, allowing a passage for the water both inside and outside the rings, thus obviating the necessity of their lifting more than one-half the space of the width of the openings in the seating, and it was found that in valves of large diameter, by increasing the number of openings, the height of lifting in opening could be further reduced; the closing was necessarily more rapid, the concussion was nearly avoided, and the passage of the water was rendered direct and free from bends and interruptions. A valve on this construction was adapted to the engine at the Lambeth Water-works, and it was found on setting it to work, that a counterbalance weight of upwards of one ton required to be moved from the pump side of the beam to some distance on the steam-piston side; the saving of steam consequent on this, and the action of the valve, amounted to about 7 per cent. of the quantity previously used. The same effect was observed at the Chelsea Water-works, where similar valves were substituted for those of Messrs. Harvey and West.

It is stated that in consequence of the galvanic action between the brass rings and the iron seatings, wood seatings were adopted, and have been found very preferable.

The dimensions of all these valves are given in detail, and also of several other large valves which have been made.

The question of the proper weight of valves in proportion to the height of the column is then examined at great length, and the following rule is given; "The mean velocity of the water in feet, per second through the valve, being ascertained, onehalf more is added to this velocity and considered as the maximum velocity of the water through the valve; and the height of the head of water being found, that would produce this velocity, every 1 inch of such height is considered equal to one ounce weight avoirdupois, acting upon each square inch of the area of the valve, against which the water impinges, in its passage to the pump barrel, allowance being made for the difference of the weight of the ring, when immersed in water, compared with its weight in the air." By this rule, it was found that a considerable weight required to be added to the valves which had been erected, and that addition rendered the concussion scarcely perceptible.

The author advocates a large area in the valve-passages for the water to flow through, in order that the power of the engine may not be expended in putting the fluid in motion to fill the pump-barrel. He states that the proper area depends on the diameter of the pump and the working velocity of the plunger; and that if the maximum velocity of the water up the suction pipe is not allowed to exceed 6 feet per second, but little advantage will in ordinary cases be gained by reducing that velocity; that an increase of speed is often unavoidable, but that it causes a great expenditure of power; and he quotes Mr. Wicksteed's experiments in support of this position. He urges from this, the importance of reducing the velocity of the water in entering and in quitting the pump barrel; and also that the lift of the valve should not exceed 2 inches, and should be as much less as possible, as the valve, in that case, closes quickly before the returnstroke of the engine commences. Short lifts are then examined, and it is stated that the valves will not close rapidly, unless they are weighted sufficiently to resist the maximum velocity of the water flowing through them, and are carefully adjusted to it; and that if they are too heavy, there is a loss of power in working the pumps.

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Several modifications of these valves, adapted to various uses, are then described, and the author states that his intention is, to lay before the Institution, an account of such valves as had been found to answer well in practice; and to direct attention to the cor

rect principles for constructing them of proper proportions and of durable materials.

The paper is illustrated by eight detailed drawings of different constructions of valves, and by three models of some which have been in use and are found successful.

Mr. Simpson corroborated the account of the advantages of the valves described in the paper; he had found them practically useful and economical.

Mr. Wicksteed said that with Messrs. Harvey and West's improvements, a valve, 4 feet in diameter, which formerly rose between 4 inches and 5 inches, now only lifted 1 inch; the concussion was diminished and the durability insured; the latter was increased by substituting wooden faces for metal ones; by this means also the corrosion, attendant upon the contact of two metals, was avoided. One of these valves had already lasted three years, and was still quite good. The principal improvement consisted in making the water pass all round the circumference, instead of through the centre of the valve. The difficulties which had been experienced at Old Ford had not arisen from the form of the valves, but from the situation in which they were placed; he argued, therefore, that when experiments were made upon these valves, new boxes and suction pipes should be made expressly for them, and they ought not to be adapted to the pipes from whence the old shaped valves had been taken. He approved particularly of the form of the double-beat valves as possessing great strength, and reducing the liability to fracture.

Mr. Taylor said that the meeting was much indebted to the author for laying down positive rules and principles on a subject which had not hitherto been sufficiently attended to. He fully approved of those forms of valves in which the area was divided into several openings; the loading the valve proportionably was also of importance. All the ring valves, among which he would include that of Mr. Hosking, tended to diminish the concussion; but however good they might appear theoretically, there were some practical objections against most of them for instance, Harvey and West's valve was not applicable for mines, because, as the two lifting faces were connected, a chip or any sand being interposed between either of them would cause considerable leakage in both; the ring valves were not liable to this objection, and therefore were preferable for mines, or situations where the water contained any foreign substances. The old butterfly leather valve had been much improved, and recently a modification of it had been introduced which promised to be very effective. The area of the valve was

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divided into eight compartments, each covered by a triangular flap of leather, hinged to the circumference of the bucket, and all meeting in the centre on a raised apex. By this arrangement nearly the whole area of the pump-valve was opened; the cost of construction was also diminished, because, instead of cutting the large flaps only out of the finest and largest hides of leather, small pieces could be used: valves thus constructed had been in use in mines for upwards of seven months without repair.

The improvements in the valves had produced a corresponding increase in the height of the column of the pumps it formerly was about 15 fathoms; Woolf had gradually increased it to 40 fathoms; and now a column of 50 fathoms was sometimes used.

He was an advocate for giving a very large area to the suction-pipes; for instance, in one mine under his direction, to a valve 20 inches in diameter, two suction-pipes, each of 20 inches diameter, had been adapted, with great advantage to the engine; the pump drew more water and worked much more steadily.

Mr. Parkes remarked, that the concussion arising from the closing of the valves of low-lift pumps, was more destructive than in the high-lifts; an entirely different system was therefore pursued in pumping. The engine started very rapidly, and was generally worked much faster, which altered the condition of the pumping. At the engine of the Waldersea drainage, near Wisbeach, there was a pump of 6 feet diameter, with a length of stroke of 8 feet, the valves were formerly destroyed more rapidly than in any mine in Cornwall; recently, Mr. Hosking had adapted to it a large box, having in the centre a valve of 30 inches diameter, and around it five other valves, the sum of the area of the six valves being greater than that of the pump: the result was a great diminution of concussion, and consequent increased durability of the valves.

Mr. Glynn agreed with Mr. Taylor in thinking that Messrs. Harvey and West's valves, were not so well adapted for mining purposes as they were for water-works, or for situations where only clean water was passed through them. Mr. Darlington had introduced a modification of the valve, which he thought would be very efficacious; it was being constructed by the Butterley Iron Company, and he would send a description of it to the Institution.

This principle of large valves had been extended to blast engines; the size of the air-valves having been much increased, a corresponding advantage had been found in their duration, as well as in the work of the engine.