Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. In some portions of the work, i.s., photography, pharmacy, micro scopy, etc., the weights and measures used therein have been retained, although not of the metric system, for it was considered that the wishes of those who would be most interested in those particular fields are, in a work like this, entitled to respectful consideration.