MY DEAR SIR,—I cannot quit the subject of Franzensbad without entering into some detail on the celebrated Mud-baths. One hears much of mud-baths at different spas of Germany: but a _genuine_ Schlammbad is _seen_ only in Bohemia, and especially at Franzensbad. The mud is obtained, as you are undoubtedly aware, from a large bog or moor, situated at the back of the Louisen and Caltsprudel wells, which, according to Dr. Kœstler, who accompanied me to examine it, is nine miles by three in extent; and he tells me also that the same schlamm extends to a _depth_ of 20 feet. Indeed the whole village may be said to be resting on this peat-earth; for you cannot dig up the soil to any depth without discovering it. The surface of the moor looked singularly black and barren; here and there, however, I discerned some yellow and white efflorescences. The yellow was by far the most abundant; and, wishing to know its composition, I collected a considerable quantity and brought it to England. It is a highly acid salt, permanently reddening litmus paper, and extremely styptic and acid to the taste. I dried some carefully; and found that 100 grains which had been completely desiccated, yielded 97.6 grains soluble in distilled water. The solution was dark brown, of the colour of beer, and contained an acid per-sulphate of iron. The remaining 2.4 grains consisted principally of iron in combination with some vegetable acid, or extractive matter. I was sorry I could not collect sufficient quantity of the white efflorescence for examination. I merely remember its _taste_ to have been equally styptic and disagreeable as the yellow. There are several minerals found in this moor. I am indebted to Dr. Palliardi (one of the resident medical men) for a good specimen of blue phosphate of iron; of the hydrated red oxyd of iron; and for one of great interest discovered _there_ by himself, termed _Kieselguhr_. This substance was first described by Professor Ehrenberg, of Berlin, to be an aggregation, or to speak more accurately, the shells of a collection of different species of infusoriæ. It is said to be pure silica—it is white; extremely light and friable, and forms one of the most beautiful objects for the microscope I have seen. I have a great quantity; and shall be happy to furnish yourself, or any friend that may desire it, with a specimen. I do not know whether you visited Dr. Palliardi’s study; it would have been well worth the trouble. He is at once a mineralogist, a botanist, an ornithologist, entymologist, chemist, and physician. I was pleased at the simplicity with which they made a mud-bath—they merely picked and sifted the mud (the sun having previously, to a certain extent, dried it) and digested it in the water of the Louisenquelle warmed by steam. The appearance of a bath when ready is anything but prepossessing; I must confess, however, on making the trial, I was agreeably disappointed.