Conjectures Concerning the Cause, and Observations upon the Phaenomena, of Earthquakes; Particularly of that great Earthquake of the first of November 1755, which proved so fatal to the City of Lisbon, and whose Effects were felt as far ar Africa, and more or less throughout almost all Europe.

First separate edition, 4to (228 X 183 mm), 71, [1]pp., folding engraved folding cross-section plate, small neat stamp to verso of terminal leaf, stitched in later sugar blue paper wrappers, preserved in a quarter calf portfolio with patterned paper boards and tie. First separate edition (having appeared in the ëPhilosophical Translationsí earlier in the year) of ìby far the most important contribution to this branch of science that has yet appeared in any language or country. Realising that the sudden development of large bodies of vapour within the terrestrial crust might start the disturbances of earthquakes, he made a great onward step in showing that successive waves would be generated in that crust, and would travel outwards, in constantly diminishing amplitude until they finally died away. It was the first time that this conception of earthquake motion had been laid before the world. With all his limitations we may yet rank him as the great pioneer of the modern science of Seismology.îóGeikie. Geikie continues: ìnot only does [the essay on earthquakes] treat of the subject of its title, but it gives an excellent account of the tectonic arrangement of the stratified formations.î This was Michellís only contribution to geological science: he also ìearned a permanent place in the history of stellar astronomy for two signal accomplishments: he was the first to make a realistic estimate to the stars, and he discovered the existence of physical double stars.îó(Dictionary of Scientific Biography). Geikie ëThe Founders of Geologyí pp. 273-77.