the dog, or in that of other animals, save so long as that fluid possesses a constitution proper, and still unknown, to the maintenance of the life of these hematozoa.

15th, The filaria invisible to the naked eye injected alive, along with the blood which transports them along the vessels. into the serous cavities, and the cellular tissue of healthy dogs, were unable to remain alive in these two new domiciles.

16th, A dog with vermiferous blood, with a female with blood not vermiferous, produces offspring, of which those belonging to the race of the father have vermiferous blood, while the others, pertaining to the race of the mother, have not.

17th, A vermiferous-blooded female dog, produced with a male dog without vermiferous blood, brings forth pups, of which those taking after the race of the mother have worms in their blood, while those resembling the father in race have none.

18th, A vermiferous-blooded female dog, with a male dog equally so, has pups with worms in their blood, whether these pups pertain to the race of the father or of the mother.

19th, The filaria in the blood of the pups have not been discovered before they have reached the age of from five to six months. The worms have continued to live in the blood of these animals, which have now reached the age of four or five years.

20th, Nineteen dogs, of which each had approximately from 11,000 to about 224,000 microscopic filaria in its blood, and also a dog having also in its blood six adult filaria, from fourteen to twenty centimetres in length, have never been seized with any special disease. Three dogs, however, having, approximately, the first 17,000, the second 25,000, and the third 112,000 microscopic filaria in the vital fluid, have been struck with epileptic-like attacks. Two of these animals died of the attacks; in the third the attacks have ceased. The health of this last dog has been perfect for more than a year, although the same number of worms always exists in the blood. Very numerous researches will yet be made on this interesting subject.*

*The author announces a new memoir on a strongylus which lives in the mesenteric arteries of the horse, and on the hematozoas, which live in the crow, the frog, and in many species of fish, and in the lumbricus terrestris or earth

worm.

Description of a Self-Acting Apparatus for preventing WaterPipes Bursting during Frost. By Mr ALEXANDER MACPHERSON, F.R.S.S.A., of Leith. Communicated by the Author. With a Plate.

It is unnecessary for me to point to the highly-injurious consequences which often result from the bursting of water-pipes with frost; or to demonstrate the great necessity there exists for some proper and efficient remedy. With the exception, perhaps, of a serious fire, there is no agent more destructive in its effects upon property than an overflow of water. It is true that such an occur

rence is frequently occasioned by the defective nature of the plumber-work; but there can be no doubt whatever, that the most prolific source of this kind of damage is due to the bursting of waterpipes with frost; and that is an event, it would seem, which the most skilfully-executed plumber-work can neither prevent nor resist.

The temperature in this country is rarely so low as to exhibit the consequences of a severe and protracted frost; and the cases of burst water-pipes have, therefore, been comparatively few. Since the winter of 1838-9, we have had no severe frost of any duration; but in that year, and others of equal severity, the water-pipes were burst all over the country, and this occasioned damage to a very large amount. While this country, however, from its temperate climate, is, in a great measure, exempted from these effects of frost, it is different in countries where a colder temperature predominates. In the northern section of the United States and Canada, this freezing of the pipes assumes a much more formidable aspect. Many of the houses are warmed with furnaces placed in the cellars or halls; and I believe one of the chief objects of this expensive precaution, is that of preserving the water-pipes from freezing.

There have been various attempts made to prevent the action of frost on water-pipes. Exterior protections of such non-conducting materials as charcoal, ropeyarn, straw, &c., have been applied to the exposed parts of the pipes, with the view of preserving the temperature. These, it is obvious, can afford but very slight protection in the event of an intense frost. It has been very generally recommended, also, as a useful precaution, to circulate the water through the pipes, by means of partially opening the cock at the sink. This, when it can be adopted with safety, is, to a certain extent, beneficial in preserving the supply-pipes from bursting; but it has been found extremely disadvantageous in freezing, and consequently obstructing, the soil-pipes and drains. From this cause, it is very often-as in New York-prevented by the municipal authorities. The attempt, which I have frequently seen made, to resist the frost by means of strong pipes, is very absurd. No strength of pipes of any material can withstand the expansive force of water while freez

ing. I may add to this, that the practice of building up water-pipes in the centre of a wall, with the view of preserving them from bursting, is dangerous in the extreme. The ill effects of the frost on the pipes is often imperceptible at the time. The expansion sustained by the pipe may not be sufficiently great to burst it; but in that case it produces a regular enlargement of the pipe, which part necessarily becomes the weakest; and it accordingly yields sooner or later to the mere pressure of the water. Cases of burst pipes in summer have thus not unfrequently to be attributed to the frost of the previous winter.

The only really practicable and unfailing means of preserving water-pipes from bursting with frost, is to adopt the simple precaution of keeping them empty. This has been well ascertained to be the only security in every country where precautions are adopted. The best of those in use at present, consists in attaching a stop-cock to the lowest part of the pipes, and another immediately above it. By the one, the water is shut off when a low temperature approaches, and by the other, the pipes are emptied of the water they contain. To render these precautions of any avail however, the utmost watchfulness is necessary, and even where the cocks exist, they are rarely used in time. Besides, a severe frost will frequently occur in course of a single night, and in that case the opportunity of shutting off the water is lost. The same objection applies to the mode of heating by fires, of circulating the water, and to all other precautions of a similar kind.

Reasoning on this, I have conceived the possibility of employing some self-acting apparatus, which, on the approach of a low degree of temperature, would of itself shut off the water and empty the pipes; or, in other words, of having a machine so constructed and regulated, that it would shut a cock before the freezing-point of water, and open it again, when the temperature assumed its normal state.

I first thought of applying a machine on the principle of the thermometer. If, in place of the small bulbous glass of an ordinary thermometer, I took a vessel of much larger dimensions, and in place of being sealed at the top, it was closed by means of a small sliding piston on the surface of the mercury;—if it were possible to adjust this, so as to elevate the piston at a temperature of 60°, it is evident that a decrease of the temperature to the freezing-point would produce a diminution of bulk in the mercury, and a corresponding descent of the piston. A stop-cock on the supply-pipe, attached to the piston-rod, might thus be made to stand open at all ordinary temperatures, and to shut precisely at the freezing point.

Such an apparatus, however, would be subject to a few serious and insurmountable objections. In the first place, it would require some intricate mechanical arrangement, to prevent it diminishing the supply of water at low temperatures, although still above the freezingpoint. In the next place, its whole available power in shutting the cock would necessarily be small, since it could only be derived from

the atmospherical pressure on the surface of a very small piston; and, lastly, it would, according to the determination of Dulong and Pétit, require about 400 cubic inches of mercury to produce one single cubic inch of vacuum in its depression between those two degrees of temperature. In short, it would not answer the purpose.

The next idea was kindly suggested to me by Sir David Brewster. It was to employ the expansion of metallic rods, on the principle of the pyrometer, to effect the same purpose; and something analogous to the original pyrometer of Muschenbrock would probably be the best adaptation. A bar of zinc, or any other expansive metal, of convenient length, may have its expansion or contraction increased to any extent, by a series of compound levers; and this might be applied as the motive power in a manner precisely similar to that described. But the mechanical difficulty of regulating the action of the pyrometer between two specific degrees of temperature again interposes; otherwise, I have no doubt but that a properly-constructed apparatus of this kind might be the most unfailing means of action I could adopt. It has these advantages over the mercury, that its power is irresistibly great, its cost would be trifling, and it would be of much easier application.

Finding these instruments to be practically inapplicable, I was driven to think of something more resembling the sudden expansion of water when freezing. It is obvious that this remarkable property of water is unlike the regular expansion of metals. What was necessary, I then thought, must be some liquid that will solidify a degree or two higher than water, and of its expansion being applied to shut off the water. Glacial acetic acid assumes the state of a solid at a temperature so high as 45°, and sulphuric acid of the density of 1.78 does the same at 46° Fahr. I was proceeding to experiment upon these, or similar bodies, when it occurred to me that of all the applications of this kind the best might be found to exist in the expansive force of water itself when freezing.

Water, according to the experiments of Boyle and Dalton, increases in bulk about one-ninth in its transition from the fluid to the solid state. This expansion occurs with an irresistible degree of force. The Florentine academicians burst a hollow brass vessel with a cavity of only 1 inch in diameter, by freezing the water it contained. The force produced was equal to 27,000 lb. Major Williams, in his experiments at Quebec, in 1784-5, besides bursting bombshells, projected an iron plug, 2ğ lb. in weight, from one of the shells, to a distance of 415 feet by the expansive force of the water it contained when freezing. These facts afford sufficient grounds for establishing the most important points of the desired motive power; those, namely, of the amount of expansion the water sustains, and the prodigious force with which that is accompanied. I calculated, that I would require in a vessel, such as I have described, 27 cubic inches of water, which would produce 3 inches of expansion, to act effectively on a stop-cock.

I therefore procured a globular glass vessel of these dimensions, accurately fitted with a cylinder and piston, and filled it with water. On exposing it to freeze, however, the water expanded equally on all sides of the vessel and burst it, instead of elevating the piston. A thin sheet brass vessel I employed for the same purpose succeeded no better. But, after a number of similar experiments, on vessels of different shapes, which I need not detail, I ultimately found that a true and accurately bored cylinder was the only vessel in which water could be frozen under pressure. This it was of great importance to ascertain; for had it occurred that ice expanded uniformly in a lateral direction it is plain that no vessel of moderate strength could have resisted the pressure. From these experiments I found that in a simple tube of any convenient dimension, fitted with a piston, it would be, without bursting, elevated by the freezing of the water it contained, and with a force far beyond what was absolutely necessary. This could be applied to shut a cock, or operate in any other manner found to be most appropriate. Such is the principle of the apparatus represented.

The only apparent objection that presented itself next, was, that the water contained in the pipes being subjected to the same degree of cold as that portion confined in the small tube, would freeze as soon, or at all events so nearly at the same time that there would not be space intervening of sufficient duration to allow of the water being shut off. This objection, however, is easily disposed of by the application of a tube possessed of superior powers of conducting heat to that of the lead pipes. Copper at once suggests itself as the most appropriate, and for two reasons: 1st, Copper is to lead, as a conductor of heat, as 18 to 89, or, as nearly as possible, 5 to 1; and, 2d, Its tenacity or cohesive power is exactly ten times that of lead. These, it will be seen, are valuable properties for the purpose, since it not only guarantees a quicker conduction of heat, or, in other words, a quicker freezing of the water it contained, but a power of resisting ten times the pressure. But there is no occasion to employ a copper tube of the same dimensions as the lead pipe. One of half, or even a fourth of the size, I have found to answer quite as well. This, again, gives a still greater advantage, since the conduction of heat holds a direct ratio to the mass of the body. In short, it is very apparent that a properly-constructed copper tube, containing a small portion of water, will be the first to freeze, and so shut off the water.

The practical application deducible from these principles, consists of a very simple apparatus. A copper tube of any convenient dimensions fitted with a piston filled with water, and firmly attached to the lead pipe, would, from its superior conducting power, be the first to freeze, and by the vertical expansion of the ice to elevate a piston and shut a stop-cock, while the water in the lead pipes was still fluid. On similar principles it would be the first to become VOL. LII. NO. CIV.-APRIL 1852.

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