Experimental researches concerning the philosophy of permanent colours, and the best means of producing them by dyeing, calico printing, etc. : vol. 1 / by Edward Bancroft.

  • Bancroft, Edward, 1744-1821.
Date:
1794
Catalogue details

Licence: Public Domain Mark

Credit: Experimental researches concerning the philosophy of permanent colours, and the best means of producing them by dyeing, calico printing, etc. : vol. 1 / by Edward Bancroft. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    fhewn, that bodies refiedt more ftrongly in pro- portion as they poflefs more phlogifton, and that the lefs refrangible colours require greater power to reflect them.” Here we have another gratuitous and firange fuppofition of an acceffion or combination of phlogifton with lead in cal- cination : I fay ftrange, becaufe thofe of the adherents of phlogifton who yet continue to be- lieve its exiftence in metals* have conftantly fup- pofed that* in calcination, while they received air, they loft, inftead of gaining, inflammable matter. But were this extravagant fuppofition to be admitted as a caufe of the changes of co- lour in metals, how can it be reconciled to any hypothefis which makes their colours depend on their refpeclive denfities ? Indeed, if the effe&s which Sir Ifaac Newton fuppofes phlogifton to have on colours were real, and if phlogifton really exifted in them, as both he and Mr. De- lava], as well as others, have until lately ima- gined, it would be difficult to conceive why all metals are not red, or more inclined to rednefs, than their calces or oxyds. But enough, per- haps too much, has been faid, to refute Mr. DelavaPs hypothefis, fo far as it relates to the colours of metals. Unfortunately, however, for my readers, as well as for myfelf, he has thought proper, in a larger work publifhed fome time ftnee, to extend the fame hypothefis to the colours of animal and vegetable fubftan- ces ; and endeavour to confirm and illuftrate Sir Ifaac Newton’s ideas on this fubjebt, by a variety of experiments, which are reprefented as in- ftanCes of changes of colour produced in thefe lubftances, by an increafe or diminution in the 4 Experimental Enquiry into the Caufe of the permanent Colours of opake Bodies, qto. fizes.