It is known that Cavendish was the first who succeeded by means of the torsion balance in effecting fairly precise measurements.

This method has been again taken in hand by different experimenters, and the most recent results are due to Mr Vernon Boys.

This learned physicist is also the author of a most useful practical invention, and has succeeded in making quartz threads as fine as can be desired and extremely uniform.

He finds that these threads possess valuable properties, such as perfect elasticity and great tenacity.

He has been able, with threads not more than 1/500 of a millimetre in diameter, to measure with precision couples of an order formerly considered outside the range of experiment, and to reduce the dimensions of the apparatus of Cavendish in the proportion of 150 to 1.