wherry: crystal form and optical properties 319 



there" I have so often discussed their development and effect. 

 There are indeed some other directions in which science is, I hope, 

 even now on the threshold of discoveries, which if they will not 

 "revolutionize warfare" will at least greatly increase the power 

 of the artillery. A famous speaker is credited with the advice to 

 a beginner, that if he could not be interesting he could at any rate 

 always be indiscreet. But in war time one is denied even this 

 resource. And so I am afraid that my contribution to your series 

 of lectures on science in relation to the war has been a story of 

 gradual development rather than of sensational advances. Even 

 so, I hope that I have been able to show you that we artillerymen 

 have maintained our traditional interest in science, and that it is, 

 not in vain that the famous statue of ''Armed Science" has been 

 for so many years the presiding genius of our mess room at Wook 

 wich. I have shown you also a little of what men of science have- 

 done for us not only in the study but in the field. I am sure that, 

 you will come forward as freely, and that my brother officers of 

 the American artillery will welcome as we have done all the assist- 

 ance that science can give them. 



CRYSTALLOGRAPHY. — Certain relations between crystalline 

 form, chemical constitution, and optical properties in organic 

 compounds, — 11.^ Edgar T. Wherry, Bureau of Chemistry. 



Penta-erythrite 



C(CH20H)4 Ditetragonal-pyTamidal; a :c = 1 : 1.024. 



The optical data given by Groth^ are tabulated here in the same 

 manner as were those of urea. (See table 4, p. 321.) 



The refraction and axial ratios agree within the limits of error of 

 measurement, so in this substance, as in urea, the standard axial 

 ratio is also the true one. 



The chemical molecule of penta-erythrite can be brought into 

 agreement with the observed symmetry if spread out around a 

 central carbon atom with all the OH groups pointing in one direc- 



<■' Continued from page 285. 



7 Chemische Krystallographie III: 385. 1910. 



