373187r
[Commentary:
This page is part of Harriot's
experiments on refractive colours. By a method of successive approximations, Harriot searches for the secondary cardinal for his glass prism, that is, the refractive index governing the secondary ray ( in the diagram on
f. 184), which, according to Harriot's theory of colour, is responsible for the appearance of colours. (As usual, the sets of four numbers are solutions of proportions: the first is to the second as the third is to the fourth, and one element is unknown, in these examples the fourth.) ]
E. pro 2aria refractione effectiva colorum.
[Translation: For the secondary refraction, which generates colours. ]
[Translation: For the secondary refraction, which generates colours. ]
Incidens 51° adfractus positus 29° 30â² 10000000 υ 39° 19â² cardinalis.
ponatur 39°
[Translation: Angle of incidence 51°. Assumed (first) refraction 29° 30â². 10000000. Sine 39° 19â² cardinal. Taken as 39° 20â².
ponatur 39°
[Translation: Angle of incidence 51°. Assumed (first) refraction 29° 30â². 10000000. Sine 39° 19â² cardinal. Taken as 39° 20â².
incidens vitreus
[Translation: Internally refracted ray incident on glass ]
[Translation: Internally refracted ray incident on glass ]
48° 49â² nimium. debuit esse 47° 56â²
[Translation: 48° 49â² too much. It ought to be about 47° 56â². ]
[Translation: 48° 49â² too much. It ought to be about 47° 56â². ]
2. ponamus igitur nouum cardinalem
[Translation: And so we assume a new, larger cardinal. ]
nimium adhuc.
[Translation: Still too much. ]
[Translation: And so we assume a new, larger cardinal. ]
nimium adhuc.
[Translation: Still too much. ]
3. Faciamus igitur nouum cardinalem paulo minorem.
[Translation: And so let us make a new cardinal, a little smaller. ]
[Translation: And so let us make a new cardinal, a little smaller. ]
4. Capiamus minorem
[Translation: Let us take a smaller cardinal. ]
[Translation: Let us take a smaller cardinal. ]
Cardinalis bonus in G
[Translation: Good cardinal, on sheet 'G'. ]
[Translation: Good cardinal, on sheet 'G'. ]