From Benjamin Rush8
ALS: American Philosophical Society
Philada: May 1st: 1773.
I am much Obliged to you for Dr. Priestley’s Experiments. They have thrown a good deal of Light upon the subject of fixed Air, Altho’ I can by no means assent to some of his inferences from them. The Experiment made with a Sprig of mint extends our Ideas of the Oconomy of Vegetables.9 But is all the fixed Air which is discharged from its various sources Absorbed and applied to the Nourishment of Plants? Does not common Air possess a power of destroying it either by Diffusion or Mixture? Is not much of it destroyed likewise by being restored to its Elasticity so as to become common Air? What water is to vapor, fixed Air appears to be to common Air. How diffirent are the Effects of Water and Vapor upon Animals, Vegetables and Fires, and yet we all know they are of the same Natures. The former possesses no narcotic stimulating or poisonous Quality, and yet Animals expire, and fires are extinguished in it. May not all the peculiar Qualities in like manner of fixed Air be ascribed to its containing common Air in a fixed state and not to any adventitious Matter of a poisonous and stimulating Nature?
The Doctor deserves great Credit for his Application of fixed Air to Medicine. To his Remarks upon this Subject I would beg leave to add One More. A large Quantity of fixed Air is discharged in Perspiration. This is proved by a Candle’s immediately ceasing to burn if it be put under the Bed Cloaths of a Person who is well covered in Bed. This fixed Air being of a recrementitious1 Nature is no doubt of a septic quality. If this be the Case we learn the great Necessity of obliging Patients to sit up as much as possible in putrid Diseases, and to change their Linnen and Bed Cloaths every Day.2
You will receive with this Letter a small Pamphlet which the public have ascribed to me. It was written at the Request of Anth: Benezet to promote and accompany a Petition to our Assembly to put a more complete Stop to the Importation of Negro Slaves into the Province.3 I have sent a Copy of it together with all those News Papers which contain the late Dispute between Govr: Hutcheson and the Counsil and Assembly at Boston to our good Friend Monsr. Dubourg of Paris. They are directed to your Care. Please to forward them by the first Opportunity.4
When shall we have the Pleasure of seeing your Treatise upon Colds?5 In Dr. Cullen’s late ingenious Arrangement of Diseases he speaks of a great many Catarhs or Colds from Contagion, but includes with these One Species a frigore.6 He does not say however that Moisture alone has any Share in producing them. I have found Shallopmen and Sailors in this City [who are] more subject to Intermitting fever, but much less to Colds than any Other People. With the sincerest Gratitude and the truest Respect I have the Honor to be Your Much Obliged Most Affectionate Humble Servant
P.S. Our Revd. Friend Mr. Coombe is to be married in a few Days, not to Miss Ord, but to a Miss Badger, an amiable young Lady with a most sweet Temper.7
Addressed: To / Benjamin Franklin Esqr / London
8. For informative annotation of this letter see Lyman H. Butterfield, ed., Letters of Benjamin Rush (2 vols., Princeton, 1951), I, 80.
9. These sentences identify the pamphlet, enclosed in BF’s letter above of Feb. 14, as Joseph Priestley, Observations on Different Kinds of Air … (London, 1772). The other pamphlet that Priestley published the same year, on impregnating water with fixed air, contained no experiments with mint.
1. Capable of being reabsorbed into the body.
2. In his answer below, July 14, BF promised to pass on this comment to Priestley.
3. The pamphlet was by Rush: An Address to the Inhabitants of the British Settlements in America, upon Slave-Keeping (Philadelphia, 1773). The petition that it supported had a transient success: an act was passed in February to double the duty on imported slaves, but was disallowed the following year. 8 Pa. Arch., VIII, 6915–16, 6937, 6965–6; Acts Privy Coun., Col., V, 398–9.
4. Rush wrote a covering letter to Dubourg, largely about the campaign against slavery; the Frenchman printed a lengthy extract from it in Œuvres, II, 315–16, which is retranslated and annotated in Butterfield, op. cit., pp. 76–8.
5. The treatise was often discussed but never written. See above, XVIII, 203, and BF’s notes below at the end of the year.
6. For Dr. William Cullen of Edinburgh see above, VII, 184 n; his Synopsis nosologiae methodicae (Edinburgh, 1769) went through a number of editions in Latin: DNB.
7. The Rev. Thomas Coombe, whom BF had known well during the young man’s recent stay in London, married Sarah (Sally) Badger on May 13; she died five years later. 2 Pa. Arch., VIII, 63; PMHB, V (1881), 30 n; VII (1883), 244.