Three sliding scales of chemical equivalents, all with same manuscripts marks, published by W Cary (devised by W H Wollaston?) all apparently of same pattern, one has 1814 date clearly, another has Jan. 1 1814 clearly.

Three sliding scales of chemical equivalents, all with same manuscripts marks, published by W Cary (devised by W H Wollaston?)

William Hyde Wollaston was a leading chemist and natural philosopher during the early 19th century. In 1813 he invented a chemical slide rule to illustrate his paper published the following year entitled ‘A synoptic scale of chemical equivalents’. He was interested in the ratio of weights of various substances used up in reactions. Positioning the slider with the weight of the substance set against it will show you the weights of other substances which will react with it. This fundamental ordering based on measurement paved the way for the periodic table of the elements, a magnificent tool in our understanding of the composition of the universe.