Schott's experiments at the Jena glass-works.
Distribution of Salinity.-A great deal of material exists on which to base a study of the surface salinity of the oceans, and Schott's chart published in Petermanns Mitteilungen for 1902 incorporates the earlier work and substantially confirms the first trustworthy chart of the kind compiled by J.
Schott's investigations show that the annual range of surface temperature in the open ocean is greatest in 40° N., with 18.4° F., and in 30 S., with 9.2° F.; on the contrary, near the equator it is less, only 4° F.
The figures given are the partial dispersions for ordinary crown and ordinary extra dense flint glasses, styled in Messrs Schott's catalogue of optical glasses as o 60 and 0.102 respectively, having refractive indices of 1 5179 and 1.6489 for the D ray respectively, and (µ D -I)/(l F -µc) =60 2 and 33.8 respectively to indicate their dispersive powers (inverted), = v.
569 in Schott's catalogue, and having µD 1.573 8 and (µD-I)/("IF-!Lc) =41'4=v, the figures of whose course of dispersion are as below: Light Flint Glass o 569.
(0.543 of Schott's catalogue) and the back lens of a crown glass, styled 0.374 in Schott's older lists.
Since the curvature powers of the positive lenses are equal, the partial dispersions of the two glasses may be simply added together, and we then have: [0.543 +0.3741 The proportions given on the lower line may now be compared with the corresponding proportional dispersions for borosilicate flint glass 0.658, closely resembling the type 0.164 of Schott's list, viz.: [0.658 (A D = I.546) 50' 11 A slight increase in the relative power of the first lens of 0.543 would bring about a still closer correspondence in the rationality, but with the curves required to produce an object-glass of this type of 6 in.
At Meran walks have been arranged according to Oertel's system, and at Llangammarch in Wales both Oertel's and Schott's systems are employed, and baths according to the Nauheim system are also to be found in London, Sidmouth, Leamington, Buxton, Strathpeffer, &c. Many people who have sedentary employments are unable to get as much exercise as they require because they have not either the time or the opportunity.