Royal Institution | Sept 15th 1832.
My dear Sir
I send you herewith an account of the three deposits not however including any notice of their peculiar striated or crystalline appearance hardness &c &c all of which you no doubt already know by inspection[.]
Temple of Serapis 1. This deposit consists principally of Carbonate of lime[.] A little sulphate of lime is present and also a little oxide of iron & Silica with alumina but all together these do not probably make more than 4 or 5 per cent. I can find no magnesia here nor any but the minutest trace of muriates[.]
Piscina Mirabile This is in chemical composition as like the last as possible[.] I do not find a word to alter[.] The state of aggregation is different & the successive deposits are not so evident; it is also more crystalline2[.]
Temple of Minerva. This substance does not contain any carbonate of lime it is essentially sulphate of lime or gypsium with a little oxide of Iron &c &c[.] This composition accounts for its crystalline appearance & other characters[.]
Your first question of "whether the first & second deposits are the same substances nearly in the same proportions" is already answered in the affirmative3[.]
Your second of "whether the combinations they contain are compatible with sea water; could they have been deposited in it?" requires a little more reservation. I cannot say that the carbonate of lime is incompatible with sea water or that it could not have been deposited from it. But I have never heard of such a deposit from the sea water we can procure now a days either naturally or during the evaporation which goes on in salt works &c &c. On the other hand they represent perfectly such deposits as are taking place continually from waters holding carbonate of lime in solution by carbonic acid and I cannot help thinking that such has been their source.
In giving this opinion I am guided merely by the appearance of the deposits & their chemical characters for I know nothing of the circumstances under which they occur although 20 years ago I happened for a few hours to be at the Temple of Serapis4.
I am | Dear Sir | Most Truly Yours | M. Faraday
Charles Babbage | &c &c &c
I have used a little as possible & return you the rest supposing you may require them. | MF
Address: Charles Babbage Esq | &c &c &c | 1 Dorset Street | Manchester Square.
BABBAGE, Charles (1834): “Observations on the Temple of Serapis at Pozzuoli,near Naples”, Proc. Geol. Soc., 2: 72-6.
BABBAGE, Charles (1847): Observations on the Temple of Serapis at Pozzuoli near Naples, London.
Please cite as “Faraday0614,” in Ɛpsilon: The Michael Faraday Collection accessed on 29 April 2024, https://epsilon.ac.uk/view/faraday/letters/Faraday0614