November 26th, ipoi.] PROCEEDINGS. xi 



cally. The mass of the star can also then be determined. The 

 matter is, however, comphcated by the fact that, whereas early 

 photographs of the surrounding nebula are not available, 

 spectroscopic measurements are now impossible. 



Professor H. B. Dixon mentioned that Mr. H. Brereton 

 B.iker had succeeded in making a mixture of hyiroyen and 

 oxygen so pure that it would not exp'ode when the vessel con- 

 taining it was raised to a red heat or when a silver wire was 

 melted in it. In one case some water was gradually formed, so 

 that the explosion of the gases would seem to depend on the 

 presence of some impurity other than steam itself. 



Professor F. E. Weiss exhibited two dwarf Japanese trees 

 which have been purchased for the Manchester Museum. They 

 y^txQ. Pinus paivifolia 7m(\ Thuja obtusa {\h.& Japanese cypress), 

 both natives of Northern Japan, where they are found at very 

 gieat altitudes and are naturally of small growth. The trees 

 exhibited, which were 30 and 40 years old respectively, were 

 only six to nine inches in height, these dwarf forms being 

 obtained by a system of starving and pruning back the plants, 

 and by contortions of the stem and branches which retard the 

 nutritive processes. 



Mr. J. E. Petavel read a paper entitled "On the 

 measurement of high explosive pressures." 



The paper was illustrated by lantern slides, and was 

 followed by a discussion, in which Professor Dixon, Dr. F. H. 

 Bowman and others took part. 



