General effects of compression, either in condensing gases, or producing solutions, or even giving combinations at low temperatures.
Light through gold leaf on to zine or most oxidable metals, these being poles—or on magnetic bars.
Transparency of metals. Sun’s light through gold leaf. Two gold leaves made poles—light passed through one to the other.
Whenever any query found an answer, he drew his pen through it and added the date. In front of the book—probably at some later time—he wrote these words:—
I already owe much to these notes, and think such a collection worth the making by every scientific man. I am sure none would think the trouble lost after a year’s experience.
A striking example had already occurred of similar suggestive notes in the optical queries of Sir Isaac Newton.
In another manuscript notebook occur the following entries under date of September 10, 1821:—
2 similar poles though they repell at most distances attract at very small distances and adhere. Query why....
Could not magnetise a plate of steel so as to resemble flat spiral. Either the magnetism would be very weak and irregular or there would be none at all.
These are interesting as showing how Faraday was educating himself by continual experiment. The explanation of each of these paradoxes has long passed into the commonplace of physics; but they would still puzzle many who have learned their science bookishly at second-hand.