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article, commending itself by its brilliancy facturers, the greatest consumers of soft soap, and transparency.

Soft soaps made from autoclaved material, and therefore very poor in glycerin, are of

will not accept a soft soap devoid of glycerin for their best materials, as the glycerin in the soap gives that soft feel and gloss which

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the glycerin has been only enriched so far that its proportion is about 10 to 12 per cent., whilst the finished crude soap glycerin as required by the refiner must contain 80 per cent., it is evident that an enormous amount of salt must fall out, before so high a concentration of the glycerin can be reached. The salt which separates out must of course incrust the vessel in which the concentration is carried out.

When the recovery of glycerin from soap lyes was first introduced, this incrustation caused such enormous trouble that for a long time the new industry was in danger of suc

tubes to complete stopping up, I have constructed a (patented) vacuum evaporator, which has been found suitable in practice for the concentration of soap lyes. An evaporator of this type-consisting of one vessel, "Single Effet "-is shown in Fig. 25. Two types of the rotating heating surface are shown in Figs. 26 and 27. From the illustrations it will be gathered that the heating surface is kept clean by means of a mechanical arrangement, so that the salt as it falls down can be drawn off with the help of the vessel attached to the bottom of the pan (Fig. 25), without it being necessary to

interrupt the boiling in the vacuum pan. In large establishments, multiple evaporation multiple evaporation commends itself on account of the greater economy. Taking advantage of the fact that up to that point when the salt begins to separate a considerable amount of water may be evaporated without fear of incrustation, I have combined in my (patented) "Double Effet" (Fig. 28), a tube evaporator with the "Single Effet" shown in Fig. 25. The soap lyes are therefore concentrated first in vessel B until they reach "salting point," that is until they reach that point at which the salt commences to separate. They are then transferred into the vessel A, in which the salt is removed as it falls out, whilst the boiling is kept up uninterruptedly. When the specific gravity of the sample has reached 13, the finished glycerin is withdrawn. The " Triple Effet" which I show in the next lantern slide is constructed on similar lines.

I exhibit here a number of crude glycerins which have been obtained by the several saponification processes described above.

All these glycerins must be purified by distillation in apparatus similar to that shown in the next slide, in order to be converted into the straw-coloured "dynamite" glycerin of specific gravity 1261 (various makes of which I show here in these bottles), and by a second distillation into the well-known water-white chemically pure glycerin.

I have endeavoured, in the limited space allotted to me, to lay before you a rapid survey of those industries which, in their aggregate, form the technical side of the fat and oil trade of this country. From the tables of imports and exports given in the first lecture, you have been able to gather the vast extent these industries have reached. Yet not only the amount of capital invested is enormous, but also a very large amount of scientific work has been done in this country in order to place these industries on a thoroughly scientific basis. Here is a branch of chemical industry which proves that this country is in the forefront, and is able to teach our friends on the Continent, and in America, a good deal yet. We are almost daily being confronted by a number of writers with the lament over the backward state of our chemical industries, and the enormous dividends paid by tar-colour manufacturers abroad are being continually held up to us. They all seem, however, to forget the large dividends which our soap and candle manufacturers are paying.

Whilst in Germany, as far as I am aware, hardly more than ten or fifteen chemists find employment in the whole soap industry proper, I know of at least two works in this country in which more than that number are engaged. If the high position which the oil and fat industries have earned by hard work, both in the factory and in the laboratory, is kept up by our young men proceeding to work in a truly scientific spirit, then we may rest assured that we shall continue to maintain the supremacy we have held so long in these industries.

Miscellaneous.

EVOLUTION OF THE MUSICAL BOW*

It is commonly accepted as a fact, which is borne out by tradition, both ancient and modern, that certain groups of stringed instruments of music must be referred for their origin to the bow of the archer. The actual historical record does not help us to come to a definite conclusion on this point, nor does the direct testimony of archæology, but from other sources very suggestive evidence is forthcoming. A comparative study of the musical instruments of modern savage and barbaric peoples makes it very clear to one that the greater portion of the probable chain of sequences which led from the simple bows to highly specialised instruments of the harp family may be reconstructed from types still existing in use among living peoples, most of the well-defined early stages being represented in Africa at the present day. The native of Damaraland, who possesses no stringed instrument proper, is in the habit of temporarily converting his ordinary shooting bow into a musical instrument. For this purpose he ties a small thong loopwise round the bow and bow-string, so as to divide the latter into two vibrating parts of unequal length. When lightly struck with a small stick the tense string emits a couple of notes, which satisfy this primitive musician's humble cravings for purely rhythmic sound. Amongst many other African tribes we find a slight advance, in the form of special rather slightly made bows constructed and used for musical purposes only. In order to increase the volume of sound, it is frequently the custom amongst some of the tribes to rest the bow against some resonant body, such as an inverted pot or hollow gourd. In many parts, again,

Extracted from the address to the Anthropological Section of the British Association, at Cambridge, by Henry Balfour, M.A., President of the Section.

"The Natural History of the Musical Bow," by H. Balfour. Clarendon Press, Oxford.

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