When I first undertook the present essays, I had confined myself to a re-publication of my fathers work, entitled, Micrographia Illustrata; but I soon found that both his and Mr. Baker’s tracts on the microscope were very imperfect. Natural history had not been so much cultivated at the period when they wrote, as it is in the present day. To the want of that information which is now easily obtained, we may with propriety impute their errors and imperfections. I have, therefore, in the fifth chapter, after some general observations on the utility of natural history, endeavoured to remedy their defects, by arranging the subject in systematic order, and by introducing the microscopic reader to the system of Linnæus, as far as relates to insects: by this he will learn to discriminate one insect from another, to characterize their different parts, and thus be better enabled to avoid error himself, and to convey instruction to others. As the transformations which insects undergo, constitute a principal branch of their history, and furnish many objects for the microscope, I have given a very ample description of them; the more so, as many microscopic writers, by not considering these changes with attention, have fallen into a variety of mistakes. Here I intended to stop; but the charms of natural history are so seducing, that I was led on to describe the peculiar and striking marks in the œconomy of these little creatures. And should the purchaser of these essays receive as much pleasure in reading this part as I did in compiling it; should it induce him to study this part of natural history; nay, should it only lead him to read the stupendous work of the most excellent Swammerdam, he will have no reason to regret his purchase, and one of my warmest wishes will be gratified. In the next chapter I have endeavoured to give the reader some idea of the internal parts of insects, principally from M. Lyonet’s Anatomical and Microscopical Description of the Caterpillar of the Cossus or Goat-moth. As this book is but little known in our country, I concluded that a specimen of the indefatigable labour of this patient and humane anatomist would be acceptable to all lovers of the microscope; and I have, therefore, appropriated a plate, which, whilst it shews what may be effected when microscopic observation is accompanied by patience and industry, displays also the wonderful organization of this insect. This is followed by a description of several miscellaneous objects, of which no proper idea could be formed without the assistance of glasses.