Continues experiments with carbonic acid and electric light [see JT's 1868-11-30], suggesting possible cause of blue cloud color and eventual whitening of light.

Asks JH to review paper on blue color of sky, polarization of skylight, and polarization of light by cloudy matter.

Clarifies letter on motion and structure modification of glaciers. JH thinks glacier ice unfavorable for exhibiting JT's phenomenon [see JT's 1856-7-30].

Is delighted with JH's exposition of colors of thin plates and of measurements of a wave of light in Familiar Lectures. Asks permission to quote from it.

Suggests experiments with regard to polarization and vaporization, and comets' tails.

In response to JH's comments on JT's explanation of comets says faintness of head and nucleus does not indicate non-existence; eye may not see all. Experiments with polarized light produce 'gorgeous' 'residual blue.'

Thanks for paper on action of rays 'of high refrangibility' on gases and vapors. Attempts to understand reflection of wave motion on particles with diameters 'incomparably smaller' than length of wave.

Corrects misinformation about refraction and dispersion of mercury ethyl and mercury methyl.

Thanks for note [see JT's 1866-5-26] on improvement of the lecturing style of JH's son [Alexander]. JH's son has studied lecture's subject deeply and loves science; JH hopes will be physics professor at a 'considerable institution.'

JT has suggested that JH's son [Alexander] be appointed to position in Royal School of Mines, but colleagues, unwisely, JT thinks, want someone more well-known.

Thanks for paper on action of solar and electric light on vapors, which should give JT further insight into blue color of sky and polarization of skylight. Comments on the latter. JH's son [Alexander] is working hard at Glasgow.

Thinks JT's work on polarization will lead to remarkable discovery. Discusses production of rainbow, parallels to Isaac Newton's explanation of black spot on a soap bubble, and problems in JT's undulatory theory explanation of reflection. In JT's experiments, what are nebulous particles produced by light in gas or vapor?

Continues experiments with carbonic acid and electric light [see JT's 1868-11-30], hoping to 'explode' idea that atmosphere's polarization is due to reflection by air particles.

Thanks for paper verifying JH's prediction that explanation of blue sky color carries with it that of polarization of skylight. Involves ultimate link between chemical and analytical dynamics. Notes that 'neutral points' in sky polarization have yet to be explained; offers tentative explanation based on clues in JT's work.

Thanks for paper on comets. Offers questions, problems to be resolved, particularly on termination of comet.

Surprised that JT cannot obtain heat spots [see JT's 1864-11-14]. Describes glasses and lenses used.

Thanks for lectures on heat motion theory and radiation through earth's atmosphere, and for brochure on 'conformation' of the Alps. Asks about upcoming lecture of JH's son [Alexander].

Thanks for and comments on papers on scientific history and molecular physics, particularly on a magnetic experiment and on dynamical efficiency of coal relative to motion theory of light and heat. Comments on nature of heat, 'vis viva.' Deplores laxity with which physicists use and confuse terms 'force,' 'motion,' and 'energy.'

Thanks for suggestion-filled letter. Remarks on blue color of water.

Regrets 'stupidity' of Italian post office, which lost note sent to JH suggesting reprinting of passage from Treatise Astr. of 1833 on operations of sun in second edition of JT's book. Also wants to publish JT's 'extremely philosophical views' on muscle contraction.