choked, as they are always liable to be from coal, dust, etc., and any new pump is subject to suspicion that it may be faulty in this respect. Some vessels have a well specially constructed to set the pump into, to prevent this danger. 1 The subject was farther discussed, and it was voted to continue it at the next meeting. The Association adjourned to the second Thursday in August. JOHN K. FISHER, Secretary pro tem. AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION, } Dr. WARREN ROWELL in the chair. AERATED BREAD. 14, 1862. Prof. Seely. The manufacture of aerated bread has recently much declined in London, England, and I should like to inquire if the aerated bread usually soon sours or molds, when kept three or four or more days after it has been baked. Mr. Fisher.-I consider all bread best when fresh, and that the "best tasting food" is usually the best for any one. I admit that almost all our preferences, as to food, are cultivated tastes; and I regard the aerated as the best bread now in common use, and believe that it keeps good the longest; but hope every one will eat what he wants while it is fresh and best, and never let it sour or mold. Mr. Dibben believed that aerated bread, made of good wheaten flour of grains in normal condition for seed, would sooner dry than mold; and that bakers could not work sour nor musty flour into it, because it would taste too plainly; and, hence, good tasting aerated bread is surety against damaged and sophisticated flour. Mr. Fisher. I believe that the reason of the London bakers giving up making aerated bread, was that it prevented them from using inferior or damaged flour, as well as prevented mixtures of beans, maize and potatoes, in what purported to be wheaten bread, as now much used both in this country and England. Mr. Dibben. I have always found that the aerated bread, as usually sold in New York, always dried, without souring or molding, when long kept in a dry place. Dr. Stevens believed that about the usual amount of fermentation in our most marketable yeast bread was very advantageous to health, especially as it then digested much easier, and thereby prevented or relieved dyspepsia. Mr. Enos Stevens admitted that the more any food is fermented or otherwise disorganized before it is eaten, the easier it will be digested in the stomach; but he had often noticed that partially disorganized food always produced tender members and tissues of the body, as feet that soon blister, hands that soon tire and falter, and brains often aching or con fused; and, therefore, he preferred and recommended unfermented food, as a requisite means of having good working limbs and all other members of the body, even if it did cost a little more labor of digestion. Prof. Seely said that many things which the theoretic chemists had declared as not containing any nourishment, had actually subsisted men and animals exclusively for years, and intimated that animal life prospered best on certain materials, but when such materials cannot be obtained then their spontaneous vitality would seem to nitrogenize mere carbonaceous vegetable matter, and use it temporarily for growth and repairs, although not so rapidly and successfully as that which was natural nitrogenous in the vegetable state. The Chairman said that dogs working on a tread mill to propel machinery did best when eating only ten per cent. of animal flesh, with the other ninety per cent. of their food the coarse flour and fine bran of sea biscuit bakery made into bread. Mr. Fisher and Dr. Stevens gave other illustrations of the use and results of various articles of food." Mr. Churchill intimated that the experiments in decarbonizing iron in reducing it from the ore, recently reported here, on further investigation, seemed not to attain more decarbonization in the preliminary process than was usual by the old process. The regular subject for discussion was called up, viz: PUMPING. Prof. Seely read the following communication from Mr. F. A. Morley, of Sodus Point, N. Y.: MODES OF RAISING WATER. What I propose to say relates entirely to the most common device for that purpose-the pump. In most of pumps, but more especially the single acting, the velocity of the column of water is constantly undergoing sudden changes; this is a great evil, as much of the power is expended in overcoming inertia, which, if it may be called friction, is by far the most important item of friction to be considered. Most of pumps, as far as the writer's observation goes, are constructed without any regard to this important point, as, for instance, a pump will have a uniform bore of four inches throughout, and a valve of three inches diameter. Now, as the water moves through the uniform size of the bore, its velocity is uniform, but as it passes the valve its velocity must become suddenly nearly doubled, and immediately subside to the uniform velocity again. There are but few exceptions to be found to this style of pump, in the whole marine list. Another point touching the inertia is the terminations of bore. It is evident that, if the ends of the bore are gradually enlarged toward their terminations, the fluid will gradually attain and lose the uniform velocity (or piston velocity) in entering and leaving the pump. (See Olmstead's Philosophy, page 293, section 429, latter part.) Mr. Fisher inquired as to using gunpowder as a motive power for * machinery. Mr. Dibben.It has been extensively experimented on, and found to be many times more expensive than steam. Mr. Fisher proposed the "Making of Common Roads," as the subject for discussion at the next meeting, which was adopted. Adjourned. ENOS STEVENS, Secretary pro tem. 1 AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION, Dr. R. P. STEVENS in the chair. Mr. J. K. Fisher read a paper as to steering vessels by means of a rudder placed in the bow. The principal advantage claimed is that it would be out of the way of the screw, and the main difficulty is to keep it firm against violent waves, and to bring it from one side to the other in changing course. He proposes to hold and to move the rudder by means of a hydraulic press. Mr. Babcock objected that a bow rudder would foul badly by drifts between the ship and rudder. Mr. Dibben objected that it would be extremely difficult to handle a bow rudder with sufficient power and speed. Mr. E- exhibited a bolt made of wire rope, so as to be elastic, and especially not to break off while holding armor plates when hit, nor while fastening standing rigging. Mr. Dibben thought that it would rust much faster than if all in one bar. ENOS STEVENS, Secretary pro tem. AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION, Mr. JOHN P. VEEDER in the chair. September 18, 1862. Mr. Fisher asked what was the speed of war steamers. Mr. Dibben.-Probably ten knots when in fighting trim; and yet sometimes, in ballast, may attain thirteen or fourteen; and commercial steamers, with strong and favorable wind, sometimes about sixteen knots. Prof. Seely explained the aspirator, an instrument through which water and air flow, adapted to aerate water, to produce cheaply a strong and steady current of air for the blowpipe, and to ventilate rooms, where a current of water is available to propel the air. A small stream of water enters the side of a larger perpendicular open tube, and, by its gravity, carries down the air in the larger tube continually, propelling out the air with great force from the bottom of the large perpendicular tube, and. taking in more air all the time at its open top. Mr. Bartlett explained the electro-ballistic machine, for testing the velocity of missiles from guns, etc. The principle of this machine is that the missile, at a certain distance, by passing through an electrical target, liberates a body to fall, or oscillate as a pendulum; and at another certain distance, say one hundred feet, hits another electro-magnetic target, and clamps or stops the falling or oscillating body; and then the distance the body fell through indicates the time that the missile was passing the space or distance between the targets. LOCOMOTION IN CITIES AND SUBURBS. Mr. J. K. Fisher.-Common carriers and liberal citizens take different views of street locomotion. The carriers look chiefly to profit, which, as they think, is most surely obtained by cheapness; liberal citizens look for some degree of comfort and decency, even though it be not consistent with extremely low prices. But while the carriers are uncontrolled, and left to the laws of trade, their accommodations will be as bad as their exclusive privileges enable them to compel citizens to endure. In expenditures that depend on their own choice, such as in their houses and stores, the citizens generally are as lavish as could be desired. But in what depends on their representatives, or those who serve them as carriers, marketers, etc., there is a less liberal expenditure. The splendor of houses and stores is strongly contrasted with the shabbiness and filthiness of streets; and the improvements in the style and cost of buildings, within thirty years, is incomparably greater than the improvements in paving; and the same comparison may be made with respect to all kinds of public vehicles. We in this Club should speak of these matters not as politicians may speak who fear to make themselves unpopular with those who tolerate the present condition of things, under the erroneous notion that they have to pay nearly the whole cost of them, and cannot afford to improve them. We should speak as men representing science, taste and progress. You will therefore excuse me if I don't tell you how a cobble pavement is laid, how an omnibus is managed, or bore you with a tame and dull account of what you already know, and would gladly forget. It will be quite enough if I say what is necessary for comparison between the barbarous systems that exist, and the system which has long been recommended by the best engineers in England, and by some of the best in this country. First, as to dirt. The quantity of dirt made per hour by a horse is not known; but fifty-five loads were taken every night from Broadway, between Bowling Green and Union Square, when it was swept under the direction of Mr. Genin. The English engineers, in evidence before parliamentary committees, offered that the comparative amount of detritus worn from pavements and roads by wheels and the feet of horses was in proportion to the iron worn from the tires and shoes; or, if there was a difference from this proportion the blows of the feet caused more than this proportion of wear. On Macadam roads, with four-horse coaches, a pound of iron was worn from the tires in the same distance in which three pounds were worn from the shoes; hence it was concluded that three-fourths of the wear was due to the feet, and one-fourth to the wheels. Marniel ascertained and reported this fact, and Macadam, Forby and others agreed with his conclusion. On the London pavements, similar to the so-called Russ pavements that are laid square with the street, a cab lost one pound from its tires while its horse lost seven pounds from its shoes. The cab at that time weighed 1,050 lbs., or about 1,350 lbs. when loaded, say a third of the weight of a loaded omnibus. Taking as unity the dirt made by the wheels of a cab, we have the following as the relative quantities worn from pavements by the different modes of conveyance we have to consider. But we have to add the manure dropped by the horses, which was found by analysis to be a third of the whole dirt. The dirt worn from the pavement by a cab and horse being equal to eight, we must add four, making twelve, one for cab and eleven for a horse. And in estimating for rail cars we may assume that one car does the work of three omnibuses, and that its wheels make no sensible amount of dirt. Therefore for This comparison shows that the street railway system by horse power, as now practiced, makes less than 29 per cent. as much dirt as the omnibus system; and that steam cars, which are likely to be sanctioned by the legislature, will reduce to nothing the ordinary dirt; and I shall show that there need not be any sensible amount of dirt of other kind from them. So far as this part of the traffic is concerned, it is satisfactory as to the dirt nuisance; but we have goods traffic and private vehicles to provide for, and it is not pretended that these can be accommodated by railways: we are still required to keep up the dirty system for this part of the traffic, and are to be relieved only from so much dirt as is made by the cars and omnibuses. I have long advocated iron flooring on the streets. No dirt could come from this floor; and the dirt thrown upon it could be easily swept clean off. On an iron floor a man could do more than a horse can do on the Russ pavement; but steam power is the cheapest, as well as the best; and I anticipate the use of steam wagons and traction engines for all kinds of traffic. And steam carriages and wagons have this advantage over the railway system, that they can be introduced without disturbance of the existing order, and can gradually displace horses, as horses and their vehicles are worn out. On stone pavements, steam carriages will make some dirt, but not of the most offensive kind: it will be pulverized granite, without manure in it. I consider that a steam omnibus will weigh one-half more than a horse omnibus, and its dirt may be represented by 41, or 13 for a steam equal in capacity to a rail car. The relative dirt will be: carriage |