Halle July 16th 57
My dear friend,
First of all I send you my best thanks for the papers containing your most recent inquiries2 which you have been kind enough to send to me. I have read them with the greatest interest. The acoustic experiments explain the condition of the phenomenon observed by Schaffgotsch3 which at first sight seemed so very curious and surprising. It loses all its mysterious qualities being reduced to a natural consequence of the battlements. One only I wonder, that of the many persons who tried to repeat the experiments none succeeded in making it with hydrogen coal. Coal-gas seemed to be undispensible. I don’t understand at all this difference (but have not yet repeated the experiments myself), you undoubtedly will know the real cause of it.
The wish to send to you the memoir here joined4 gives me the immediate impulse to write to you. You find in it a series of experiments which I had already begun in Marburg5 and which then had been interrupted by the inquiry on the thermic pleochroism of crystals.6 The present paper, which as you see, is not large of size contains the most difficult and troublesome experiments I ever made. The difference in the quality of radiant heat being reflected from various metals is a very small one and can be discovered and be expressed by numbers to be relied upon, only by the most scrupulous attention and carefulness. But by the practice I believe to have got in experiments on radiant heat and by the 17000 observations I have made with the thermomultiplier7 only for the results contained in this paper ‘on the influence of metals on radiant heat,’8 I have not a shadow of a doubt in the theses pronounced in it, which differ from all which—by Melloni’s9 authority—until now was settled in the compendium books.
I take the liberty to add one copy for Prof. Faraday as a little mark of my high esteem and veneration, and another for our common friend, Hirst, of whom I have got (besides the memoirs he has been kind enough to send to me and for which I address my best thanks to him) no further news since your stay in Halle.10 I beg him to take the paper as a testimonial of my unaltered friendship. I have much thought of him. How may be Mrs Hirst?11 Has her health allowed her to return to his first abode and his former occupation in England?
I don’t know whether you have heard that Prof. Kohlrausch12 had got a professorship in Erlangen.13 They have given him no successor in Marburg, but to do at least something for Physicks they have made Prof. Gerling ‘Geheimer Hofrath’14 and have given him an assistant! You see ‘good old Timer’15 has come back to Marburg! O my dear Marburg!
My lecture in Halle is now distributed for the whole of Physicks so that I treat optics and heat in Summer; the rest (mechanics, acoustics, magnetism, electricity) in Winter. I had first 4, now 30 hearers. You must go to Bonn16 for the Naturforscher Versammlung17 to counterbalance Plücker18 (16 Sept, as I know). I can not leave Halle. And now good bye! My little John (Johannes)19 remembers himself kindly to Dr. John Tyndall, the friend of his father.
Yours | most faithfully | Herm. Knoblauch.
RI MS JT/1/K/20
RI MS JT/1/TYP/7/2499–9A
Herman Knoblauch: Hermann Knoblauch (1820–95), a German physicist and chemist known for his contributions to the studies of radiant heat. He co-authored two papers with Tyndall in 1850, Tyndall’s first scientific publications (ADB).
the papers containing your most recent inquiries: possibly J. Tyndall and T. H. Huxley, ‘On the Structure and Motion of Glaciers’, Phil. Trans., 147 (1857), pp. 327–46; and the abstract of Tyndall’s most recent Friday evening lecture, ‘On M. Lissajous’ Acoustic Experiments’, Roy. Inst. Proc., 2 (1854–8), pp. 441–3.
Schaffgotsch: Franz Schaffgotsch (1816–64), a German scientist. See F. B. Schaffgotsch, ‘Akustische Beobachtungen’, Poggend. Annal., 101 (1857), pp. 471–87; and Count Schaffgotsch, ‘Acoustic Experiments’, Phil. Mag., 14 (1857), pp. 541–4. Tyndall recounts his and Schaffgotsch’s similar experiments in acoustics in Sound: A Course of Eight Lectures (London: Longman’s, Green, and Co., 1867), pp. 226–30.
the memoir here joined: missing.
Marburg: Knoblauch was a teacher of Tyndall’s at the University of Marburg (see letter 1399, n. 10), and they published two papers together on diamagnetism. See R. Jackson, ‘John Tyndall and the Early History of Diamagnetism’, Annals of Science, 72 (2015), pp. 435–89, on pp. 443–50.
thermic pleochroism of crystals: pleochroism is the phenomena in which crystals exhibit different colours depending on the angle at which light reaches the crystal (OED). Knoblauch investigated the way heat was transmitted through crystals depending on the angle of incidence. See H. Knoblauch, ‘Ueber die Abhängigkeit des Durchgangs der strahlenden Wärme durch Krystalle von ihrer Richtung in denselben’, Poggend. Annal., 161 (1852), pp. 169–88; and ‘Ueber die Abhängigkeit des Durchgangs der strahlenden Wärme durch Krystalle von ihrer Richtung in denselben’, Poggend. Annal., 169 (1854), pp. 161–212.
thermomultiplier: early name for a thermopile (OED).
‘on the influence of metals on radiant heat’: H. Knoblauch, ‘On the Influence of Metals upon Radiant Heat’, Phil. Mag., 14 (1857), pp. 356–74.
Melloni’s: Macedonio Melloni (1798–1854), an Italian physicist and 1834 recipient of the RS’s Rumford Medal, ‘For his discoveries relevant to radiant heat’ (CDSB).
Halle: Knoblauch moved from the University of Marburg to the University of Halle in 1853, where Tyndall must have visited him.
Mrs Hirst: Anna Hirst. She had died on 1 July.
Prof. Kohlrausch: Rudolph Kohlrausch (1809–58), a German physicist who taught at the University of Marburg and the University of Erlangen (CDSB).
Erlangen: University of Erlangen.
‘Geheimer Hofrath’: privy councillor (German).
‘good old Timer’: not identified.
Bonn: a city in western Germany.
Naturforscher Versammlung: the thirty-third meeting of the Versammlung der Gesellschaft Deutscher Naturforscher und Ärzte was held in Bonn in September 1857.
counterbalance Plücker: Julius Plücker. Regarding Plücker and Tyndall’s relationship, see letters 1299 and 1360.
My little John (Johannes): Johannes Knoblauch (1855–1915), mathematician and son of Hermann Knoblauch (NDB).
Please cite as “Tyndall1414,” in Ɛpsilon: The John Tyndall Collection accessed on