THE PREFACE

The following Sheets are therefore drawn up as an Explanation of these Copper-Plates, and 'tis hoped they may even make them better understood than they could be by the Doctor's own Accounts ; which must be ac- knowledged (with all due Regard to the Memory of so great a Man) to be frequently tedious and obscure, as well as so unmethodical, that to se- veral Figures no Descriptions can possibly be found, but by turning over the whole Book, there being no Direction at all to guide us to them.

It was necessary to form these Explanations from the Work itself where- to the Plates belonged, but the Disposition, Stile, and Manner, will be found entirely new : Whatever properly concerns the same Subject being here brought together, from the different Places where scattered and in- termixed throughout the MICROGRAPHIA, and expressed with the ut- most Brevity and Plainness of Language.

This renders the present Volume so small : though it really contains the whole Sense of all that is necessary fully to understand the following Plates. And nearly one half, even of this Little, consists of new Dis- coveries or Observations, made since the DOCTOR's Time, on the several Subjects which the Figures represent : whereby a great Variety of Natural History is conveyed to the READER's Hands, in a narrow Compass and at a small Expence.—The Plates themselves will be found also more in- structive, by engraving over every Figure an Account of what it is, and of the Page where we may look for the Description of it.

Little more is requisite than to inform the Reader, that the Mi- croscope Dr. HOOKE used was of the Double-Kind ; but much more cumbersome, and less convenient, both as to its Structure and Apparatus than what our Opticians make at present. For this Instrument (that new Sort particularly which has very lately been constructed on an improved Plan) is brought now to such a Degree of Perfection, that no Observer need be apprehensive he shall be unable to discover, and that too very easily, any of the minutest Parts of Objects which the Doctor could dis- cern with the Microscope he employed.

The Doctor sometimes mentions the comparative Size of Objects when magnisied by his Glasses ; and therefore, as the Curious may very naturally enquire by what means he could compute their Bigness, it seems proper to acquaint them with the Method whereby he took their Measure.—Having (he tells us) rectified the Microscope, to see the desired Object through it very distinctly ; at the same time that he look'd upon the Object through the Glass with one Eye, he looked upon other Objects at the same Di- stance with his other bare Eye : by which means he was able, by the Help of a Ruler divided into Inches and small Parts, and laid on the Pedestal of the Microscope, to cast, as it were, the magnified Appearance of the Object upon the Ruler, and thereby exactly to measure the Diameter it appears of through the Glass ; which being compared with the Diameter it appears of to the naked Eye, will easily afford the Quantity of its being magnisied.