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THE AMERICAN NATURALIST [Vol. LIII 



sophical Discoveries and Hints, than in most extant of 

 its bulk." It contains the first study of the fantastical 

 colours ' ' of thin plates with a partial explanation by in- 

 terference; a theory of light as a ''very short vibrating 

 motion" transverse to straight lines of propagation 

 through a ''homogenous medium" (p. 56). Heat is 

 stated to be "a property of a body arising from the 

 motion or agitation of its parts" (p. 37) ; Fluidity is "but 

 an effect of a very strong and quick shaking motion, 

 whereby the parts are, as it were, loosened from each 

 other, and consequently leave an interjacent space or 

 vacuity" (p. 41); while ideas in regard to combustion 

 are clearly outlined (p. 103) which foreshadow those 

 reached by Mayow. 



But the biologist's interest in the "Micrographia" is 

 chiefly in Hooke 's application of his improved compound 

 microscope (Fig. 2) to the study of animals and plants. 

 At this time Malpighi, Grew, Leeuwenhoek and Swam- 

 merdam were engaged in studies, with simple lenses or 

 compound microscopes, on the secrets of the finer struc- 

 ture of organisms which were to give them higher rank 

 in biological history than Hooke 's desultory work in this 

 field. Hooke, as has been said, was interested primarily 

 in demonstrating the usefulness of his microscope and 

 his belief that in inventions for the "improvement of 

 the senses" lay the key to a more profound understand- 

 ing of nature. This he accomplished and therefore, en- 

 tirely aside from the other remarkable qualities of the 

 "Micrographia," the book holds a unique place in the 

 history of biology. It paved the way, as it were, for the 

 more special, profound and methodical studies of the 

 contemporary founders of the morphology of organisms 

 by creating a considerable interest in microscopy, and in 

 addition ]:»roved to be for over a century the standard 

 source from which writers on the microsco])e gleaned 

 much infonnation niul many figures.'^ 



