Page:Proceedings of the Royal Society of London Vol 4.djvu/418

Rh " To His Royal Highness Prince Albert of Saxe Cohurg and Gotha, K.G., F.R.S., Sec.

" The Humble Address of the President, Council, and Fel- lows of the Royal Society of London for improving Natural Knowledge.

" May it please Your Royal Highness,

" We, the President, Council, and Fellows of the Royal Society of London for improving Natural Knowledge, beg to be permitted^ on the present occasion, to offer to Your Royal Highness our con- gratulation on the providential escape of Her Majesty and Your Royal Highness from the murderous attack of an assassin.

" That the same Almighty Arm may continue to preserve Her Majesty and Your Royal Highness from every danger, and from every evil, is our most sincere and earnest prayer."

A paper was read, entitled, " On the Specific Inductive Capacities of certain Electric Substances." By William Snow Harris, Esq., F.R.S.

The author, pursuing the experimental inquiry suggested by the theory of Mr. Faraday relative to the differences in specific induc- tive capacity exhibited by different dialectric substances, instituted a series of experiments for determining with precision their compa- rative powers of insulation, and of sustaining by induction charges of electricity. The substances to be examined were cast into the form of circular plates and furnished on both their surfaces with circular coatings of tinfoil of a diameter equal to one-half that of the plate, and the electric intensities were measured by electrometers of the same construction as those which he used in his former experiments, and which he has described in his papers already published in the Philosophical Transactions for 1859. The results are stated in ta- bles ; from the last of which it appears that the inductive capacities of the dialectric bodies tried, that of air being expressed by unity, are proportional to the following numbers : —

Substances. Relative capacities.

Air 1

Rosin 1*77

Pitch 1-8

Bees' wax 1*86

Glass 1-9

Brimstone 1*93

Shell-lac 1-95

The author, in conclusion, offers some observations on the expe-