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than one reason for thinking so. The journal of this machine, when we first tried it, was found not to be exactly right, and the maker promised to make one that should be exactly right. It was sent on to us as being about as good a thing as they could make. We found, in running, that the journal, instead of having its edge parallel with the axis, was crowning. That was the best they could do in making a perfect machine, I suppose; and, in order to make it fit the bearing, we had to scrape out the bearing. The effect was shown on the metal. After running a while, it left a very bright place in one spot; after it was run some little time longer, it left a bright place in another spot, and we had to scrape the box to fit the unshapely journal. But after getting it right it will not stay right. Again, the tendency of a weight bearing on an unsupported shaft end is to bend the shaft. That is not a very great defect, because the shaft is tolerably stout, and the unsupported end is short; but still there is a tendency that way, and that tendency of course increases the tendency to vibrate in the direction of the shaft. I hope that sometime, by the help of more ingenuity than has been brought to bear upon this subject yet, there will be a good machine to determine friction by heat, and there will be another to determine it by the lubricating power merely. In order to determine it by the lubricating power, we must use a certain measure of oil every time; so many drops, of the same size, of course: or we must use a certain weight, so many milligrammes, and use it until it is worn out. With the heatmachine we could keep the oil in excess all the time, and thus get rid of some of the objections which lie against distribution, or make distribution much more perfect. I should like to have the results of a heat-machine of the right character. I believe the thing can be brought about; and yet you will find, in all the machines that have been produced, from the first one down, an enormous mass of metal not insulated. Some of them have no provision for registering the temperature. Two of those before us have thermometers; but what do their indications amount to? In order to have any thing like accuracy with either of these machines, it will be necessary to have the room in which the machine is used at precisely the same temperature, and not to open a door or window while the experiments are going on. It would be a great deal better to have a machine. that can be insulated than to insulate the room.

I should say, in passing, that there is, in one of the late numbers of the "Engineer," a description of a machine which presents some very good points; but it is liable to some of the objections I have already mentioned. It is a disk-machine, however, and it is the latest thing of the kind, I believe, which has been constructed; yet there is room for criticism. It is easier to criticise, I must say, than it is to make the thing as it ought to be; still, there has been improvement, and there may be improvement which will go still further.

QUESTION. Will you be kind enough to state the percentage of divergence when you changed that, and undertook to put it back in the same way?

Professor ORDWAY. In two successive trials, we find that the coefficient of friction will be six pounds at one time, and nine at another. It is so great a divergence that it is perfectly absurd to suppose that both of them can be correct. It is customary for some people, in cases of this kind, to take an average; but an average of errors will never do. Two wrongs will not make a right; but people frequently go on that principle. They would try a series of experiments, and get as the result of one six pounds, another nine, another seven, another five, take an average of them, and call that right. But I don't think any of them would be right, with this machine as it is. We have found that this machine is useful only for one thing, and that is to test the fluidity of oil; and fluidity can be tested without the use of an expensive machine. We had already determined fluidity by a very simple instrument indeed, which any glass-blower can make in two minutes. We simply take a glass tube, and blow a bulb in it like that, and make a very narrow outlet, and suck up the oil until this bulb is full, and then let it run, and count the number of seconds that it takes to run down to this point. In that way we can determine fluidity with precision. Of course, the temperature must be the same. Of course it is necessary to surround this pipette in such a way as to insure a uniform temperature, to know precisely at what temperature the trial is made, which is an important thing.

In addition to what I said in the other Report, of the value of the chemical test, I have one observation to make. In testing olive oil and lard oil, we get a very good indication as to the goodness of the oil, or the amount of adulteration by nitrosulphuric acid, as it was called by Mr. Roth. This is made by

passing nitrous fumes into sulphuric acid, at 46° B., for eight or nine days. We have found that by adding one or two per cent of nitric acid to the sulphuric acid at 46° B., we can get as good results in ten minutes as we can get in ten days by the other method; and, although Mr. Roth recommended this liquid as likely to keep for many months, we find that it deteriorates. We found that some made not long ago had lost its efficacy entirely, and it had to be charged up again with nitrous fumes, which, however, could be done in a few moments. The best test of the excellence of olive and lard oil, I believe, is this one. If you stir up this Roth's liquid, properly made with olive oil, it solidifies in an hour or two. Other oils will not solidify; and, if there is an admixture of cotton-seed oil, it makes the pasty mass which I explained in the former Report.

There is one point to which I wish to allude, not because I have made any experiments, but because there may be some popular fallacy respecting it. Some people think they can judge of oil by the feel of it. If an oil feels greasy, it only shows that there is something in it of the nature of the oil of our skin.. Petroleum oils may not have that peculiar feel, and yet they may be very good lubricants. We must remember that point, that what dissolves oil may still be a good lubricant. It has the property of dissolving away that oil, and not leaving one which is precisely equivalent to what we are accustomed to. Hence, I think you may be deceived sometimes in judging of petroleum oils. They do not quite agree with the skin; they will not touch it, and do not lubricate it in the same way that the human fat does.

I mentioned in a former Report that we had found sperm oil, in all the various trials we had made, to be a very valuable oil. We have not had time ourselves to investigate this subject; but two of the young men who are about to graduate from the Institute have had the matter of sperm oil under scientific investigation, and I hope in a few weeks we shall have some results which will be worth something. The peculiar composition and character of sperm oil are matters which have never been fully investigated by anybody. These young men have found that there are some important substances in sperm oil, which are not to be found in ordinary oils.

I heard, after the Report last autumn, that I had spoken a good deal of "saponification," which, being a chemical term,

everybody did not understand. I mentioned some of our trials of saponification, which had reference to the oils for greasing wool. You all know that it is desirable to have, for that purpose, an oil which can be removed from wool with little trouble, after the wool has been carded and spun and woven.

an oil which will saponify readily. By "saponification," we mean making the oil into a soap, which is really soluble in water. That is the old-fashioned explanation. As we explain it nowadays, it is the decomposition of the animal or vegetable oils into stearate, oleate, and palmitate of soda, or potash, and glycerine. Lard oil is a compound of oleic and stearic acids and glycerine. This compound, however, is not very easily decomposed. We have to boil lard oil for a long time with. caustic alkali, in order to effect the decomposition. There is a wonderful difference in oils, with respect to the ease with which this decomposition takes place. Sperm oil saponifies with great difficulty, and it is a better oil for lubricating purposes, for the very reason that it is not so readily decomposed as others. On the other hand, it would be very unsuitable for oiling wool, for the same reason. It will not be quickly dissolved in alkali, and taken away from the wool. Those oils which saponify most easily are the best for oiling wool. For instance, if we take lard oil, and separate the oleic acid, that oleic acid, having once been formed, is readily dissolved by caustic soda, or common carbonate of soda. That is the reason why oleic acid or red oil, which is so much used, is a superior article for oiling wool. It is not a compound which requires to be broken up.

There are some scientific points connected with this, which I am not prepared to say much about, because we have not had time to investigate them. I believe red oil is the best oil for oiling wool; but there is the difficulty of spontaneous combustion. How this can be remedied, I do not know. People talk about saponifying petroleum; but it is utterly impossible to saponify petroleum oils, because the petroleum does not consist of an acid and a base, or any thing comparable with glycerine. There is nothing in petroleum which can be made to combine with potash or soda. People who talk of saponification, in connection with petroleum, are deceived by considering emulsionation as saponification. You may stir up petroleum with potash or soda, and it will emulsionate; it will form a milky liquid; it will become suspended, and may remain in that condition a

month or two: but that is not saponification. The petroleum will finally separate unchanged. The great question seems to be how much petroleum oil may be mixed with red oil, and be mechanically removed from the woven cloth by emulsionation. I cannot say that I have experimented far enough in that direction to be able to answer the question. Sperm oil consists of something besides glycerine. Glycerine oxidizes very readily in the air. For instance, if we take linseed oil and expose it to the air, in a very short time the glycerine in it begins to oxidize. Linseed oil contains a peculiar acid, called linoleic acid; and, when it is exposed to the action of the air, the glycerine is all oxidized, and disappears as acetic, formic, and other volatile acids. That is one reason why lard oil and olive oil, which are disposed to oxidize, become rancid so much more readily than some of the animal oils, which contain less glycerine. Sperm oil contains some, but it contains chiefly a base which has less tendency to decompose by exposure to the air. And there is one oil, that Mr. Atkinson will speak of pretty soon, that has still less tendency to decompose, and that is an oil which comes from sheep's wool. Sheep's wool has no glycerine in it. It contains cholesterine in the place of glycerine, and cholesterine has no tendency to oxidize. And that is the reason why the oil in sheep's wool is not prone to spontaneous combustion.

So far, I may say that our experiments on oils have resulted mainly in demonstrating that it is important to have an oil that is not particularly volatile, and which is free from sediment; and, at the same time, the thinner we can get it for spindles and the like, the better. But it will not do to thin it down with light oils, petroleum or any thing else, which will volatilize: we must thin it with something that has no tendency to evaporate whatever. We can only accomplish that by the means I have before mentioned, by mixing a fixed oil with it. The question is, which fixed oil it should be. Sperm oil is less liable to oxidation than some others, and it would seem to be better on that account. Sperm oil is lighter, thinner: it has less specific gravity than some other oils, and it is a little more suitable on that account, perhaps.

QUESTION. What effect will be produced by mixing gum with a mineral oil?

Professor ORDWAY. It will, of course, tend to increase its adhesiveness, or cohesion. It will make it more like tar; and,

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