brewer's barm, but was quite unsuccessful, for reasons already given. I next had recourse to the liquid ferment then, and still supplied by barm companies to bakers for baking bread; but with this I also failed, in consequence of the absence of both quantity and quality. There was little solid matter in a gallon, and that little was decidedly deficient in life and power. Experiments were then commenced on distiller's yeast, and I found this was really the true source from which supplies were to be obtained, if the article was to be prepared in this country. In connection with this fact, I may take the present opportunity of expressing my thanks to Messrs Menzies, Bernard, and Craig, of the Caledonian Distillery, for the kind and ready manner in which they furnished me, from time to time, with the raw material for the purpose of experimental inquiry. The distillers' yeast is undoubtedly, up to the present time, so far as I know, the only source from whence we can draw material for the purpose of making a solid yeast, in every respect equal to the German yeast, so extensively sent over to England by our foreign neighbours.

The second, and certainly the most important point connected with this mauufacture, and one which I think has been completely overlooked in any previous research, is the ascertainment of the precise and proper time for the removal of the crude yeast, from the surface of the vats. In my previous communication, I have already stated that the diastase of the malt effects, during its infusion with other grain, under certain conditions, the conversion of starch into sugar, in a manner similar to that in which this substance effects the same change during the germination of the seed in the ground, whereby the insoluble starch of the seed becomes the soluble saccharine matter, capable of affording nourishment and support to the young and tender plant. Now this transformation of starch into sugar in the distiller's hands is merely one step in the process; because he now induces fermentation by the addition of yeast, in order that the sugar in its turn may become broken up, and by a wonderful change of its elementary constituents, pass into alcohol and carbonic acid gas. This process commences of course almost immediately, when the proper

arrangements have been made, and begins in a liquid containing, say, 44 lbs. of saccharine matter to every 36 gallons of wort. The disappearance of sugar and the substitution of spirit is called attenuation; and when healthy and perfect, this process goes on until there is no more sugar, and the liquid is then ready for the still. The yeast, having nothing more to do, falls to the bottom of the vat, and becomes useless. This I put thoroughly to the test, but found the albuminous mass difficult to work, and so inert as a ferment, that nothing could be made of it for baking purposes. It would therefore be naturally concluded, that when attenuation had been about half completed, and when the action was going briskly on, that this would be the proper time to skim the yeast. Such, however, is not the fact; because at this stage, solid yeast, though carefully prepared, was found to be useless in the hands of the baker; and not to dwell longer on this point, I may at once say, that, as a rule, the strongest and most effective yeast is to be got when the saccharometer shows that nearly all the sugar has been decomposed; or in other words, we have the paradox of the yeast plant, when just about to finish its labours, and fall as a useless substance, proving itself at that particular time, better and stronger for the purpose of being manufactured into solid yeast than at any other. This statement is most important, because I am satisfied, if unattended to, no process which can be followed will ever prove satisfactory in its results.

We now come to the consideration of the third point :

Supposing we are fairly started on a sound basis, by having skimmed or drawn off our raw material in a proper state, and at the precise time when it is in the best condition, it becomes necessary to take its specific gravity. This is also important, because it is amazing how yeast differs as to the solid matter it contains. Ranging from 12 oz. to 2 lb. I found to be the minimum and maximum weights of solid matter in each imperial gallon. The yeast must first, however, be carefully strained before being thus weighed, in order that husks, &c. may be got rid of, and then, having taken its specific gravity, it requires to be well and repeatedly washed in pure cold water until every impurity is removed. When all extraneous

matter has thus been washed away, there will still be found adhering a certain quantity of acid, which can only be effectually removed by the addition of alkaline preparations. In connection with this part of the subject, I tried a great many experiments, and found more than one substance answer the purpose; but after repeated trials I am disposed to give a preference to the pure crystalline sesqui-carbonate of ammonia. The proportions of this salt to be used must depend upon the amount of acidity present, as well as the quantity of solid material you have to operate upon; and which has been ascertained, as just recommended, by taking the specific gravity of the raw material after it has been got from the fermenting vat. Of course the saturation and removal of acid can be known by the usual appliance of test papers, &c. The last water employed for washing away the acid from the yeast ought to be slightly sweetened with sugar. When this has been done, and most of the liquid poured off, what remains is to be thrown on a cloth filter, and allowed to remain there, until the soft pulpy mass is ready to be placed in an ordinary screw-press, surrounded with plenty of cloth; and when sufficiently pressed, may be removed, broken up, and packed into canvass bags ready for use. It may be proper to state here, that at times, when certain kinds of grain are employed in fermentation, a dark-coloured yeast is produced, which, being offensive to the eye, is at once rejected by the consumer. In the course of my investigations, I made several efforts to overcome this, and was to a certain extent perfectly successful. I found more than one harmless combination, from the use of which I was able to bleach or whiten the yeast thus discoloured-but with this drawback, that in every case the introduction of such substances lessened the fermentive power of the yeast; and this being of course an insuperable objection, I need not farther refer to the agents employed.

Having now got the German yeast prepared, allow me to refer to the fourth point, viz. the best mode of preserving it. And here there is not a little difficulty. Warm sultry weather, electricity in the atmosphere, damp, want of free access of air, rough usage, carelessness in packing, too much moisture in the yeast itself, keeping (however carefully) beyond a cer

tain time—all or any of these will cause hasty and certain decomposition. I have thought and tried, and tried and thought again, of some means by which the liability of this substance to spoil might be overcome. I need not tire you by recounting successes and failures, but give you the result; viz., that while solid yeast may be hardened so that it will keep longer than the German preparation, yet in no case can this be done without detracting from its power as a fermenting agent; and those various experiments have led me to the conclusion, that the Germans have been prevented from using any such means, just in the same way that they have been foiled in drying and reducing their famous yeast to powder, so as to make it a more portable article, than it is ever likely to be. Many, I know, have surmised that the foreign yeast is regularly mixed with some farinaceous substance. My own impression is, that such is not the case, but that the yeast imported is simply the result of fermenting certain grain, the barm produced from this being collected and prepared in a similar manner, as has been already described. Like many other processes, great care and nicety are required in the manufacture, as it is something quite marvellous how a little neglect will destroy the whole vitality of this substance. Fresh healthy yeast, collected at the proper point of attenuation, and prepared according to the directions already given, packed and treated with ordinary care, and placed where air will circulate freely round it, will, I am satisfied, keep as long as the German, and prove equally powerful and useful for baking purposes. Place either German or Scotch made solid yeast in a cask or box, or otherwise exclude the air, and certain destruction awaits it; and hence the reason why no yeast ever arrives from Holland or Germany in any other than canvass bags placed in open hampers.

Having now glanced at the best manner of preparing solid or German yeast, it naturally follows that I should make some special allusion to the reasons why the manufacture of this article has not been already successfully established and carried out. Before doing this, I may be permitted to state, that, till October last, I was now and again engaged making this article, and sending out samples to those districts in England where I

knew there was a steady demand for German yeast. Of many of these samples I received the best accounts; while several loaves of bread were baked here from each quantity of yeast I produced, and the bread so baked was a great favourite with all who tasted it. Several noble and influential families in the country wrote more than once for small supplies, and one and all testified as to its goodness and usefulness in baking; as a consequence, I had applications from dealers in England, who would have contracted for several tons a week, had I been able to undertake their orders. But probably the most convincing proof of the fact that this substance could be prepared on the spot is to be found from the following circumstance. A German, who for fifteen years has supplied a certain district in England with Dutch yeast, entered into correspondence with me on the subject, and had several bags sent him from time to time, in order that he might distribute samples among his customers. At length I sent him the last sample bag I intended he should have, requesting his opinion of the merits of the same, and now give you an extract from his letter in reply, which is dated 12th September 1860:

"The bag came duly to hand, and am glad to say it turned out all right. I was not able to give you a report respecting the strength yesterday, as I had to wait for the result after the baking process. I arranged, therefore, with a baker last night, to have it fairly tried against the Dutch barm, and was present till two o'clock this morning at the bake-house; to watch proceedings. Now the result is, that the Dutch sponge began somewhat earlier to rise than the sponge made with your lot; but after half an hour's working it kept pace together, and the two sponges were ready for the dough at almost the same time. In fact, we cannot find fault with the sample, and I trust you will soon be able to bring forward a competitive article. The bread I saw this morning was very good, and no difference could be observed when comparing the one with the other." Then follows an order for several baskets, and a proposal to contract for stated supplies. I might have added more evidence of a similar nature, but it would answer no purpose, because the above was perhaps the most severe test