The following treatise, which is one of the five histories mentioned in the Mistoria Naturalis^ was published in 1658 hy Dr. Itawley. A good deal of its contents occur in an imperfect and fragmentary state in the Phenomena UniversOIt has somewhat the appearance of having been left unfinished, and excepting a table of specific gravities and an account of the way in which this table was constructed, contains little that is now of interest. The table occurs also in the PJiczmmma Uhiversi: in tho Ristoria Demi et llari one substance is omitted and six added, so that the whole number of substances men-1 One of the fragments published by Cruter in 1651, which will be printed in Part III. of tliis edition. My own impression is that much of the first portion of the present treatise - from tho (irst tabula, down to the monilum, p 63.-is of earlier dato than Grutcr"s copy, and less perfect; and that tho remainder only-extending from the first cunnexio to the end-is to be regarded as the HisTable of Contents ristobia densi et KAKI; Prêðàñå to the HrsTORiA Densi 12ò Rari, by Robert; Lesde"Ellis9; Hcbtoria Dknsi et Rari27; inqutsitio de magnete 119 topica inquisitionis de luce et lumine 127; sylva sylvarum; Prkfacr to tbe Sylva Sylvarum, by Robert Lksliu; ELLrs143; Sylva Sylvarum159; Tablk ok the Experiments479About the Publisher Forgotten Books is a publisher of historical writings, such as: Philosophy, Classics, Science, Religion, History, Folklore and Mythology.Forgotten Books" Classic Reprint Series utilizes the latest technology to regenerate facsimiles of historically important writings. Careful attention has been made to accurately preserve the original format of each page whilst digitally enhancing the difficult to read text.