Addressed to a German Princess; Vol. II.
These letters continue the previous discussion, before returning to physics where electricity in its infancy is investigated. Methods of measuring longitude are detailed, and there is a lot of discussion about magnetism. There is a return to optics, where lenses and various applications such as microscopes, telescopes, etc. are investigated. Finally, some astronomical questions are presented.
Plate IV Figures.
Letters I - IX : The discussion of vol. I is completed.
Letters X - XVII : Monads : Can matter be divided indefinitely or not?
Letters XVIII - XXII : Thoughts on colours, sound and light, the human voice.
Letters XXIII - XXIX : Principles of Electricity.
Letters XXX - XXXIX : Leyden jar; phenomena involving electricity incl. lightning.
Letters L - LV :The Longitude.
Plate V Figures.
Letters XLVI - LIII: Ways of measuring longitude.
Letters LIV - LX : The Compass .
Letters LXI - LXXI : Magnetism.
Letters LXXII - LXXXI : Dioptrics .
Letters LXXXII - LXXXIX : Lenses and simple optical instruments .
Plate VI Figures.
Letters XC - XCVIII : Optical instruments cond'd.
Letters XC1X - CIX : Lens defects and corrections.
Letters CX - CXIX : Phenomena relating to atmospheric Refraction.