The latter commenced or dates from the second half of the twentieth century, when it was first discovered how to produce aluminium in large quantities from common clay, old tiles, potsherds, china, and earthenware." "Ah!" said I, "here, then, we have another striking example to teach us that discoveries simply arrived at by purely scientific processes searched after from the pure motive of increase of knowledge, may often be ultimately productive of the greatest practical use. The same metal which for years after Wöhler's discovery continued to be a curiosity--so much so that a few grains of it were preserved among the collections of chemical preparations--has now become universally beneficial, nay, a perfect godsend to those districts where clay, i.e. aluminium ore, is the only underground wealth." Following up this idea, at the risk of being ridiculed or, perhaps, reprimanded for my impertinent garrulousness, I continued in the following strain: "Think of the phosphorus discovered by Brandt and Künckel as early as 1669, yet never getting into common use until the lucifers, fusees, and 'flamers' made their appearance some two hundred years afterwards; and of chloroform, now the greatest alleviation of suffering humanity, although Dumas, when he first compounded it, did but little dream of its application. Then, again, when Sir Humphry Davy's remarkable experiments taught him the refrigerating power of metal gas, did this not ultimately lead to the invention of the safety lamp? and not only has the latter already preserved thousands of human lives, but, more than that, the principle of Davy's invention has actually become the basis upon which all steam-engines are constructed, as well as those by which ice can be made at any time. With regard to the invention of the art of photography, how could it have become a reality, a possibility, without the number of purely scientific discoveries that preceded it; aye, purely scientific discoveries, such as Porta's so-called camera obscura [3] (sixteenth century); Scheele's discovery of the discoloration of chloride of silver by light, at which he did not arrive until two hundred years afterwards; Courtois's finding of the iodine, 1811; or the invention of gun cotton, from which Schönbein learned to make collodion; nor would it be difficult to name several other materials, all found by regular chemical processes, to fix the photographic images, and to make them permanent." Encouraged by my companion's "line of non-intervention," I ventured to continue to speak my thoughts aloud.