Holland believed that the addition of acids to the brine was an innovation based upon the mistaken idea that the use of acid accounted for the superiority of the Dutch salt, but at the time at which he wrote the practice had been discontinued in Cheshire. Animal jelly and gluten for clearing the brine and promoting the separation of the earthy contents, were much used in preference to blood, which, while excellent for the purpose when fresh, was difficult to procure in sufficient quantity and to preserve from putrefaction. White of eggs, glue, and jelly procured by boiling cows’ and calves’ feet, were also found to answer perfectly well for the purpose of clarifying brine, but the use of new or stale ale and beer grounds as a brine clarifier, had been abandoned as inefficacious by Cheshire salt-men. Dr. Brownrigg was of opinion that salt-boilers had little to plead in favour of the addition of butter during the evaporation process, beyond immemorial custom, but Holland considered the salt-makers had ample grounds for their belief that butter assisted the granulation of the salt and made the brine “work more kindly.” On the question of the addition of alum opinions varied. Lowndes ascribed the superiority of his salt to the use of alum, but Brownrigg declared that “the goodness of Mr. Lowndes’ salt does not seem to be owing to the alum with which it is mixed, but may be attributed chiefly to the gentle heat used in the preparation.” [Illustration: WITTON BROOK, NORTHWICH. SUBMERGED TRACT OF AGRICULTURAL LAND] Holland combated the general impression obtaining at the time, that salt formed from the same brine varied by the application of different degrees of heat, not only in external appearance but also in quality, and the equally prevalent idea that salt formed from natural brine was inferior in its power of preserving animal flesh to bay-salt. He proved by quotation and experiment that such prejudices were entirely unfounded, and proceeded to show that the action of bay-salt is exactly similar to that of the large-grained salt, and that neither variety has any advantage over the salt prepared by a boiling heat except in the size and compactness of its crystals and in its containing a somewhat smaller proportion of the water of crystallization; and as the large-grained fishery salt is more than equal to the bay salt in these important points, it at least equals the latter in its power of preserving animal flesh or provisions.