But even if an efficient method of room heating is introduced, our room will not warm up quickly if the walls consist of material of low insulating quality or of high thermal capacity. There is on record an outstanding example, of this. A room lined with plaster usually took about an hour and a-half to warm up to comfort levels in the winter mornings. When, however, the lining was supplemented with oak panelling, the same gas fire was able to warm the room adequately in half-an-hour. The panelling improved the insulation of the room, but more important, being constructed of a material of low thermal capacity, its temperature rose much more rapidly than did the plaster. In consequence, radiant heat was retained to the room more rapidly and the room reached a level of comfort much more quickly. The development of new types of wall-linings having these desirable characteristics is fraught with difficulty, because other factors must be kept to the fore. Of these, cheapness of manufacture and ease of application are of prime importance. There is a big field for a young physicist in this domain. But with the present shortage of qualified men interested in classical aspects of the science, progress must necessarily be slow and results delayed.

X-Ray Diffraction Of Ironsand. By N. J. Rumsey, M.Sc., Dominion Physical Laboratory. New Zealand's ironsands, particularly those on the west coast of the North Island, have long been regarded as a potentially rich source of iron. Now their relatively high titanium content has aroused considerable interest, and their smaller vanadium content is also considered worth attention. The sands consist of grains of many different minerals. The proportions of these vary from place to place, even from one part of a beach to another; and the South Island ironsands differ very considerably from those of the North. In the North Island sands, the mineral present in quantity from which iron should most conveniently be extracted is magnetite (Fe3O4), and as this is strongly magnetic it can readily be separated almost completely from the other materials. The grains of magnetite are found to contain one-tenth as much titanium as iron, and a small quantity of vanadium.1 This unusually large proportion of titanium is the main reason for the failure of past attempts to work the sands.2 In a blast furnace titanium forms heavy infusible slags which accumulate at the bottom and soon put the furnace out of action. No method of reducing the titanium content before sending the magnetite to the furnace has yet been devised. Monro and Beavis1 concluded from chemical evidence that the titanium atoms are actually in the magnetite lattice, i.e., some of the lattice points normally occupied by iron atoms are occupied by titanium atoms. This arrangement is known to occur in some minerals in other parts of the world. Chemical evidence alone, however, cannot settle this matter, and the only way of obtaining the necessary further information is to apply the methods of X-ray crystallography. The apparatus used to do this is that designed by Williamson and constructed at the Dominion Physical Laboratory.3 It consists of an X-ray tube with interchangeable anticathodes and the necessary pumps and power supplies, and a Debye-Hull powder camera. The method requires substantially monochromatic X-rays. These are obtained by strongly exciting the characteristic K radiation of a suitable metal used as the anticathode or target, and removing the unwanted Kβ line with a suitable filter. The material to be studied is ground up to a fine powder, bound together with a gum containing only light atoms, and formed into a very thin rod which is slowly rotated at the centre of the camera (with its axis vertical) while a narrow (horizontal) beam of monochromatic X-rays