[47] V. Chapter on Books, and on Geography.
[48] Dr. Darwin. Zoonomia.
[49] At the end of the History of Vision.
[50] "Nov. 7, 1749. Electrical fluid agrees with lightning in these particulars. 1. Giving light. 2. Colour of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell. The electric fluid is attracted by points. We do not know whether this property is in lightning. But since they agree in all the particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made."
Dr. Franklin's Letters, page 322.
[51] Helvetius, "Sur l'Esprit."
[52] See preface to L'Esprit des Romains considéré.
[53] See the account in the Monthly Review.
[54] He had tried to sing it to the tune of "Hope, thou nurse of young desire."
[55] Priestley on Vision, vol. i. page 23.