BRITISH ASSOCIATION MEETING. 



451 



generation, so extinction has been concomitant with creative power, whicli has 

 continued to provide a succession of species ; and so far as the varying forms of 

 life which this planet has witnessed, there has been an advance and progress in 

 the main. 



Geology demonstrates that the creative force has not deserted this earth during 

 any of her periods of time, and that in respect to no one class of animals has the 

 manifestation of that force been limited to one epoch. 



In the reflection that at how late, and in how brief, a period of historical time, 

 geological knowledge has been acquired, we must feel that, vast as it seems, it 

 may be but a vei^ small part of the patrimony of truth destined for the possession 

 of future generations. 



Comparing the realities of the Association in its labours with the " Solomon's 

 House" of the "New Atlantis," and the realities of our national and private 

 observatories, our museums, our learned societies, and zoological, botanical, and 

 horticultual gardens with its imaginary departments, it seems as if we were realising 

 that grand philosophical dream, or prefigurative vision of "the father of modern 

 science." We can scarcely appreciate the rate of progress of human knowledge 

 unless we go back for an instant to that period which is thus chosen as the 

 starting-point of this survey. 



From Bacon's treatment of the Copernican theory we are passed onwards to 

 Galileo's invention of the telescope and the discovery of the four small moons 

 revolving round Jupiter, the analogy of vfhich to the Solar system as conceived by 

 Copernicus, gave the " holding-turn" to the opinions of mankind respecting the 

 heliocentric system ; and hence we are progressed through the first observations 

 of the transits of Mercury and Venus across the sun's disk, and those other 

 observed facts upon which the motions of the heavenly bodies have been deter- 

 mined and the laws which regulate them made out, to those more abstruse inves- 

 tigations on the laws of gravitation and those other difficult problems which are 

 now being worked out. 



The progress of knowledge of another form of all pervading force, w^hich wo 

 call from its most notable effect on one of the senses, light, has not been less 

 remarkable than that of gravitation. 



Galileo's discovery of the satellites of Jupiter supplied Romer with the data 

 for measuring the velocity of light. Descartes, in his theory of the Rainbow, 

 referred the different colours to the diflerent amount of refraction, and made 

 a near approximation to Newton's discovery of the colours entering into the 

 composition of the luminous ray, and of their different refrangibility. Hook, 

 and Hughens, and Newton, entered into explanations of the phenomena of light, 

 and the names of Young, Malus, Fresnell, Arago, Brewster, Stokes, Jarmin, 

 and others, have been successively associated with the discoveries of achromatism, 

 of the laws of double refraction, of polarization, circular and elliptical, of dipola- 

 rization, and those later advances of optics which have realized more than Bacon 

 conceived might flow from the labours of his " perspective house." Some of the 

 national sciences, as we now comprehend them, had not germinated in Bacon's 

 time. Chemistry was then alchemy ; Geology and Paleontology were undreamt 

 of ; but magnetism and electricity had begun to be observed and their phenomena 

 compared and defined, and entitled to be regarded as the first step toward a scien- 

 tific knowledge of those powers. 



It is true that long before the 17th century the magnet was known, and the 

 compass had guided the mariner's bark through trackless seas, but to Gilbert is 

 due the observation of the phenomena that electricity attracted light bodies, while 

 magnetic force acted upon iron only. 



A century later the phenomenon of repulsion was detected. The conduction of 

 electric force and the diflerent behaviour of bodies in contact lending to their 

 division into conductor and non-conductor next followed. The definition of two 

 kinds of electricity, negative and positive, formed an important stop, which led lo 

 a brilliant series of experiments and discoveries, with inventions, such as the 

 Lpyden jar for intensifying the electric shock. The instantaneous transmission 

 of electric force, the application of the lightning conductor, the association, as be- 



