Showing 5 results

GA does not think WW's letter to David Brewster 'at all savage': 'If I had any discussion with Brewster on these points I would certainly hit him about his bad information and his influence in acting on it. The revenues of professorships &c is one point already reproached - another is the character of the professors "Whewell, Airy & Hamilton" the only true experimenters - Does not [James?] Cumming do more than all? And did [Sir W. R. ?] Hamilton since he drew vital air ever make or meditate an experiment or trouble himself about other peoples?...I wish Babbage's non-lecturing could somehow be lugged into this controversy'.

Calais - JH has told the printers to send WW the proofs of his article on light ['Treatise on Light', Encyclopaedia Metropolitana, 1827], and is very obliged to WW for undertaking the superintendence of the press in his absence. JH has been careful with the history: 'I do not want to take on myself a task so insidious as balancing the merits and settling or even stating the claims of men so jealous as Brewster and Biot and Arago'.

Royal Observatory Greenwich - Gives an account of the difficulties involved in constructing a self-registering machine to measure terrestrial magnetism: 'There is only one way in which I can conceive the possibility of such a machine, namely by making the magnet carry a point, and constructing [a] mechanism which should lift the paper up to the point to receive a dot and then withdraw the paper that the magnet might quietly make up its mind as to the position that it would take for the next dot: this to be repeated as often as necessary, say every minute. Taking into account the horizontal oscillation, the up-and-down-bobbing &c of the magnet, which may be checked, I think this may be mechanically possible: but what shall the dot be?' - there are problems with the different possible inks. Is puzzled by David Brewster's latest work - 'it amounts to this, that light from different parts of the spectra can interfere. This is quite opposed to all analogy'.

Royal Observatory Greenwich - Answers WW's queries: when Newton's 'analysis is carried to perfection (i.e. so as to shew Fraunhoffer's lines), it has certainly developed original properties of light... Their existence in the diffraction spectrum tends most strikingly to confirm this. - You may also say that persons who have tried the experiments with great care do not believe in [David] Brewster's changes of colour. - The changes of colour are certainly the only source of his objections'. The French have always associated Thomas Young with the discovery of the undulating theory of light.

The Brighton Road - Belated thanks for WW's account of Stevin's [Simon Stevin] investigations about the composition and resolution of forces. JH finds what WW says of Stevin agreeable to what Lagrange says. JH has not been employed in experiments on polarization for some months, and instead has been 'familiarizing myself with the known phenomena, and acquiring that practical habit of experimentation without which it is useless to attempt anything new'. [David] Brewster's discovery of more than one polarising axis in various crystals is a most important discovery, and completely upsets [Jean Baptiste] Biot's division of doubly refracting crystals into attractive and repulsive. JH gives a description of his inquiries and where his experimental observations differ from Brewster's: 'I observed that the phenomenon of the miniature polarised rings which Brewster spoke of in a former paper, was very different in appearance and position from what his description had led me to expect'. Instead 'of one set of ellipses, complete or nearly so seen along the axis, I saw two half sets cut off across their conjugate axes, and equally distant from the axis of the nitre prism'. Brewster places nitre among the class of salts with two axes, and JH has observed three and even contiguous sets of rings.