The paper covers a period of little more than two years in the early history of the Royal Institution, but it is the period in which the house in Albemarle Street was purchased and Count Rumford devoted all his energies to establishing in it the Institution he had conceived. The house was enlarged and adapted to its new purpose; at first a temporary and later the well-known lecture theatre were built. The first Resident Professor and lecturer in the new theatre was Thomas Garnett, whose brief and unhappy connection with the Royal Institution is recorded.

The conventional view of the prehistory of Newton's synthesis in the Principia of his predecessors' work in planetary theory and terrestrial gravitation is still not seriously changed from that which Newton himself chose to impose on his contemporaries at the end of his life. In his own words:

‘… the same year ‘1666’ I began to think of gravity extending to ye orb of the Moon & having found out how to estimate the force wth wch [a] globe revolving within a sphere presses the surface of the sphere from Keplers rule of the periodical times of the Planets being in a sesquialterate proportion of their distances from the centers of their Orbs, & having deduced that the forces wch keep the Planets in their orbs must [be] reciprocally as the squares of their distances from the centers about wch they revolve: & thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the earth, & found them answer pretty nearly …’

References to the stars permeate the writings of Paracelsus (1493–1541); yet modern authorities comment on the way he restricted astrological influence. The contradiction is only apparent, and disappears when the significance he attached to the relevant vocabulary is understood. He had in mind a kind of influence rather different from that usually thought of in connection with astrology, and the astrological jargon he bandied about had a metaphorical more often than a literal meaning. In his major works, signs of detailed interest in the movements of the actual stars are few; the ‘astrological’ terminology hides a system of natural explanation by virtues or forces largely immanent in earthly objects.

The preceding paper described how all-pervasive was the influence that Paracelsus designated ‘astral’. In what sense, then, is it true that he placed restrictions, on astrological powers? The restriction applies to the more limited and usual sense of astrology, referring to the control of events on earth by the stars in the sky. Paracelsus was not prepared to hand over our fates entirely to a distant autocracy of the stars quite beyond our control.

There is a wealth of source material to be digested by the historian. From about 1800 onwards books and specialized scientific journals have appeared in ever-increasing numbers, and he may feel overwhelmed by the printed sources. But printed material can supply only a part of the information he needs. The printed word of a scientist rarely shows how he arrived at his concepts, why they took the turn they did and what influences contributed to their formation and development. For these the historian must turn to private papers, to correspondence, to laboratory notebooks, diaries, drawings and designs and to whatever other record of day-by-day thinking may have been kept.