Geoffrey Martin

Law governing the Connexion between the Number of Particles and their Diameters in grinding Crushed Sand

THE discovery of a simple law relating to continuity of particle size in fine grinding (or the breaking up larger into smaller particles) has long been a matter of scientific and technical importance. By means of experiments extending over some years, the British Portland Cement Research Association has definitely ascertained that, so far as a crystalline substance such as “standard sand” is concerned, a definite law does undoubtedly exist, which may be defined mathematically as follows:

The Peltier Effect and Low-temperature Research

I WAS much interested to see Mr. A. A. Campbell Swintons letter to NATURE of February 24, p. 828, on the above subject. So far as I am aware, the first suggestion to attain low temperatures by means of the Peltier effect was made by me when a student some twenty years ago. If Mr. Campbell Swinton will look up NATURE of August 15, 1901, p. 376, and also the Chemical News, 1901, vol. lxxxiv., p. 73, he will see an article by myself entitled “On a Possible Method of Obtaining the Absolute Zero of Temperature”, in which the method is suggested in detail. There is little doubt that a great field of research would open out once the absolute zero of temperature were obtained, and temperature as a phase vanished from matter.

“Mathematics” applied to Chemistry

IN his notice of my book “Researches on the Affinities of the Elements” in NATURE, November 16, the reviewer impugns the legality of applying mathematical formulæ to my surfaces. I trust I may be allowed to answer briefly my critics objections. His difficulty as to the non-continuous nature is imaginary, and arises from a mistaking of the object to be achieved—which is simply to obtain either a surface or a mathematical expression from which can be deduced the affinities any one element exhibits for any other. This can be done from the formulæ, and they do, therefore, characterise the chemical properties of an element which depend upon these affinities. Although there exist an infinite number of points on the surface which are occupied by no element, yet there exist only a finite number of points the x and y coordinates of which are whole numbers, and to every integer value given to x and y in my formulæ there corresponds a definite element; so that, so long as we keep within the domain of integer numbers (as we are forced to do by the nature of the construction) continuity is attained.

Rock Pressure at Great Depths

IN his address to the engineering section of the British Association, Mr. Parsons speaks of sinking a shaft into the earth for a distance of 12 miles.