Propiolic acid may be printed along with aniline-black, catechu brown and drabs, and with alumina and iron mordants for madder colors.

After the indigo-blue is fully developed, the mordants are fixed in the ordinary manner, dyed with alizarin, padded with Turkey-red oil, steamed, and otherwise treated as usual.

Indigo-blue, whether natural or artificial, suffers by prolonged steaming at high pressure. For this reason only such steam colors can be associated with propiolic acid as may be fixed by short steaming at low pressure.

No. 2.-On Prepared Cloth (for Full Shades.)

Dissolve 2 lbs. of xanthate of soda in 1 gallon of cold water. Pad the goods with the above, dry, print with standard, and after printing follow the above treatment. The pieces may also be first printed with xanthate and then covered with standard. Alumina and iron mordants for madder colors may be likewise printed on cloth thus prepared, or printed with xanthate of soda.

The potential importance, from a purely commercial point of view, of the manufacture may be judged of by reference to the following statistics, showing that the annual value of the world's growth of indigo is no less than four millions sterling.

Estimated Yearly Average of the Production of Indigo in the World, taken from a Total Crop for a Period of Ten Years.

How far the artificial will drive out the natural coloring matter from the market cannot, as has been said, be foreseen. It is interesting, as the only instance of the kind on record, to cast a glance at the history of the production of the first of the artificial vegetable coloring mattersalizarin. In this case thre increase in the quantity produced since its discovery in 1869 has been enormous; such, indeed, that the artificial color has now entirely superseded the natural one to the almost complete annihilation of the growth of madder root. It appears that

whilst, for the ten years immediately preceding 1869, the average value of the annual imports of madder root was over 1,000,000 sterling, the imports of the same material during last year (1880) amounted only to £24,000. The whole difference being made up by the introduction of artificial alizarin. In 1868 no less a quantity than 60,000 tons of madder root were sent into the market, this containing 600,000 kilos. of pure natural alizarin. But, in ten years later, a quantity of artificial alizarin, more than equal to the above amount, was sent out from the various chemical factories; so that in ten years the artificial production had overtaken the natural growth, and the 300,000 or 400,000 acres of land, which had hitherto been used for the growth of madder, can henceforward be better employed in growing corn or other articles of food. According to returns, for which the speaker had to thank Mr. Perkin, the estimated growth of madder in the world previous to 1869 was 90,000 tons, of the average value of £45 per ton, representing a total of £4,050,000.

Last year (1880) the estimated production of the artificial coloring matter was 14,000 tons, but this contains only 10 per cent. of pure alizarin. Reckoning one ton of the artificial coloring matter as equal to 9 tons of madder, the whole artificial product is equivalent to 126,000 tons of madder. The present value of these 14,000 tons of alizarin paste, at £122 per ton, is £1,568,000; that of 126,000 tons of madder, at £45, is £5,670,000, or a saving is effected by the use of alizarin of considerably over 4,000,000 sterling. In other words, we get our alizarin dyeing done now for less than one-third of the price which we had to pay to have it done with madder.

Our knowledge concerning the chemistry of alizarin has also proportionately increased since the above date. For whilst at that time only one distinct body having the above composition was known, we are now acquainted with no less than nine of the ten dioxy-anthraquinones whose existence is theoretically possible, according as the positions of the two semi-molecules of hydroxyl are changed.

Of the nine known dioxy-anthraquinones only one, viz., alizarin, or that in which the hydroxyls are contained in the position 1, 2, is actually used as a coloring agent. Then again, three trioxy-anthraquinones, CHO2(OH), are known. One of these is contained in madder root, and has long been known as purpurin. The other trioxyanthraquinones can be artificially prepared. One, termed anthrapurpurin, is an important coloring matter, especially valuable to Turkey-red dyers as giving a full or fiery red. The other, called flavo-purpurin, gives an orange dye with alumina mordants. All these various coloring matters can now be artificially produced, and by mixing these in varying proportions a far greater variety of tints can be obtained than was possible with madder alone, and thus the power of diversifying the color at will is placed in the hands of the dyer and calico printer.

It is quite possible that in an analogous way a variety of shades of blue may be ultimately obtained from substituted indigoes, and thus our catalogue of coal-tar colors may be still further increased.

To Englishmen it is a somewhat mortifying reflection that whilst the raw materials from which all these coal-tar colors are made are produced in our country, the finished and valuable colors are nearly all manufactured in Germany. The crude and inexpensive materials are, therefore, exported by us abroad to be converted into colors having many hundred times the value, and these expensive colors have again to be bought by English dyers and calico printers for use in our staple industries. The total annual value of manufactured coal-tar colors amounts to about three and a half millions; and as England herself, though furnishing all the raw material, makes only a small fraction of this quantity, but uses a large fraction, it is clear that she loses the profit on the manufacture. The causes of this fact which we must acknowledge, viz., that Germany has driven England out of the field in this important branch of chemical manufacture, are probably various. In the first place, there is no doubt that much of the German success is due to the long-continued attention which their numerous universities have paid to the cultivation of organic chemistry as a pure science, for this is carried out with a degree of completeness and to an extent to which we in England are as yet strangers. Seeondly, much again is to be attributed to the far more general recognition amongst German than amongst English men of business of the value, from a merely mercantile point of view, of high scientific train

ing. In proof of this it may be mentioned that each of two of the largest German color works employs no less a number than from 25 to 30 highly educated scientific chemists, at salaries varying from £250 to £500 or £600 per annum. A third cause, which doubtless exerts a great influence in this matter, is the English law of patents. This, in the special case of coloring matters at least, offers no protection to English patentees against foreign infringement, for when these colors are once on the goods they cannot be identified. Foreign infringers can thus lower the price so that only the patentee, if skillful, can compete against them, and no English licencees of the patent can exist. This may, to some extent, account for the reluctance which English capitalists feel in embarking in the manufacture of artificial coloring matters. That England possesses, both in the scientific and in the practical direction, ability equal to the occasion, none can doubt. But be that as it may, the whole honor of the discovery of artificial indigo belongs to Germany and to the distinguished chemist Professor Adolf Baeyer, whilst towards the solution of the difficult problem of its economic manufacture, the first successful steps have been taken by Dr. Caro and the Baden Aniline and Soda Works of Mannheim.

Influence of Varying Pressure upon Pendulums.— M. Saint-Loup finds, as a first result of his experiments upon the influence of atmospheric pressure upon the duration of pendulum oscillations, that there is an increase of about of a second per day for a fall of ten millimetres in the barometer. He does not attach much importance to this figure, regarding it merely as an indication of the order of magnitude of the disturbances; but it seems to show the importance of a correction for pressure in all calculations of exact time. Tresca states that when the conference was held, under the direction of Le Verrier, for the construction of three Parisian regulators of precision, one of the constructors, M. Redier, had fitted to the pendulum a metallic barometer, with an arm which was displaced so as to compensate the variations of retarding influence in the atmospheric pressure.- Comptes Rendus.

C.

UNIVERSAL ENERGY OF LIGHT.*

BY PLINY EARLE CHASE, LL.D.

Professor of Philosophy in Haverford College.

Force is generally regarded as a function of mass and velocity. The greatest known velocities which can be produced by central forces are wave velocities. The greatest known wave velocity which appears to be universally diffused is the velocity of light.

=

=

=

=

=

=

Let v velocity of light; v = circular orbital velocity at Sun's surface = goro v3 Earth's mean orbital velocity; v, velocity of Sun's equatorial rotation; u = potential velocity of water at 0°C. = V2gX100X13896 ft.; u = potential velocity of water at its maximum density; u, potential velocity of water evaporation 1/2g×536 37×1389.6 ft.; mp, m3, M5, m = masses of Sun, Earth, Jupiter, Saturn; h, Earth's semiaxis major; h height of mean oscillatory projection due to the combining energy of H2O; t = time of acquiring circular orbital velocity at Laplace's limit of synchronous rotation and revolution = time of rotation÷2; to = time of acquiring "nascent "nascent" or dissociative velocity at nucleal surface π μ time of rotation = t; x = Weber's electro-chemical unit; = electro-magnetic unit; = total magnetic force; terrestrial magnetic force; t = present value of t, at Sun's surface; g, gravitating acceleration at Sun's surface.

=

The simplicity of the relations of the universal velocity (vx) to other physical velocities is shown in the following equations:

* Abstract of a paper read before the American Association for the Advancement of Science, August, 1881.