296 



SCIENCE 



[N. S. Vol. LII. No. 1343 



than 8 cm., or if it falls more than 11 cm. 

 With increasing size of drop aU of these dis- 

 tances increase. Thus the lower limit of the 

 range of sounding which is marked A on the 

 figure is about Y.O cm. for a drop which has a 

 mass of 45 mg., but is between 7.7 cm. and 7.8 

 cm. for a drop which has a mass of 49 mg. 



iO 



45 



10 



I I 



Tig. 1. 



The depth of the water into which the drop 

 falls makes no difference so long as this depth 

 exceeds about three centimeters. The hori- 

 zontal distance from the boundary of the 

 water surface to the point at which the drop 



strikes makes no difference so long as this 

 distance is more than about a centimeter. 

 The depth of the water surface below the top 

 of the containing vessel appears to be with- 

 out effect. 



Instead of the characteristic sharp click of 

 the drop there was occasionally a softer, duller 

 sound, and when this soft sound occurred the 

 drop often left a bubble at the point where 

 it had struck. In the ease of the click no 

 bubble was usually left. 



I have no explanation to suggest for this 

 series of sounds. If they depended on the 

 shape of the drop when it struck the water 

 we should not expect an abrupt boundary be- 

 tween the regions of sounding and the regions 

 of silence, and we should expect the series of 

 regions to repeat at distances proportional to 

 the squares of the successive integers. 



Arthur Taber Jones 



Smith College 



THE CRYSTAL STRUCTURE OF ICE 



: X-RAY photographs of ice were taken to de- 

 termine its crystal structure following the 

 method used by A. W. Hull.^ The lines on 

 the film correspond to those of the hexagonal 

 system. They show that ice has a lattice which 

 is built up of two sets of right, triangular 

 prisms interpenetrating one another in the 

 following way. Consider the plane contain- 

 ing the bases of one of the sets of prisms. 

 The molecules lie at the vertices of equilateral 

 triangles of side 4.52 Angstroms. At a dis- 

 tance of 3.66 Angstroms above this plane lies 

 the plane containing the bases of the second 

 set of prisms. Here the molecules also lie at 

 the vertices of equilateral triangles equal to 

 those of the first set, but each molecule is 

 situated directly above the center of one of 

 the lower triangles. The other molecules of 

 the crystal will lie directly above the mole- 

 cules of the two planes just described at inter- 

 vals of 7.32 Angstroms. The above values give 

 an axial ratio of 1.62 in good agreement with 

 the crystaUographer's value of 1.617.* From 



iPhys. Eev., 9, 85, January, 1917. 



2 Gtmelin Kraut, ' ' Handbuch der Anorganischen 

 Ohemie," HeidellDerg, Vol. I., 1, p. 107, 1907. 



