Faraday to Charles Babbage   29 December 1838

R Institution | 29 Decr 1838

Dear Babbage

The following fixed oils do not thicken by cold or if they do at all but very little

Almond

Linseed

Sessimun [sic]

Castor - CD.

The Linseed oil of course unboiled[.] The Sessimun oil may be obtained at some druggists it is used to adulterate almond oil. The castor oil should be that having the commercial mark C.D. other castor oil will solidify more or less. Of these the Almond is the most fluid the Castor the least fluid i.e. thickest.

None of these are very dear in the large way. Even the Castor not more perhaps than 1/6 per pint[.]

As a further assistance to you I may say that spirits of turpentine or the distilled caoutchouc fluid added even in small quantities to some oil thins them much & counteracts the effect of cold more or less[.] But then being volatile, they would evaporate in time though slowly¹[.]

Ever | Most Truly Yours | M. Faraday