gems, density, specific gravity

The many applications that can be made, for the purposes of natural philosophy, from the relationships which bodies bear to one another through their respective specific gravities engaged my attention some years ago, prompting me to collect all experiments of this kind I encountered in the course of my studies, along with several new ones of my own. When my collection began to grow substantial, I arranged the various substances into tables according to their species—a method I found most convenient, as it allowed additions to be made anywhere without disturbing the overall structure. This arrangement also made the tables easy to consult and well suited for making immediate comparisons among bodies of the same kind. Now, having no further opportunity to enlarge my collection, I take the liberty of recommending the continuation of this work to others, as a subject well worthy of the attention of some members of the Royal Society, to whom I now present these tables in the hope they may prove of some use and service to the inquisitive and philosophical part of the world, as I persuade myself they truly will—particularly when they shall be further rectified by omitting erroneous or uncertain experiments; when they shall be enlarged through the addition of others found in reputable authors or still lying unpublished in the collections of the curious; and especially if certain gentlemen of skill, leisure, and opportunity will be pleased to supply the remaining defects by sharing their own observations on those substances whose specific gravities have not yet been carefully recorded.