subsequent research. His " law " of boiling points is no longer 

 regarded as an accurate expression of experimental facts, and his 

 deductions with respect to specific volumes have been largely affected 

 by subsequent work. It has been conclusively shown that molecular 

 volume is not a purely additive property. There is no longer room 

 for doubt that the molecular volumes of substances are affected by 

 far more conditions than Kopp was able to take cognisance of. 



The value CH 2 = 22 has no other significance than as expressing 

 the average increment in volume in successive members of a homo- 

 logous series. Indeed, as the physical data increase, it becomes 

 doubtful whether even this mean value is correct. Later observations 

 appear to show that the value augments as the series is ascended. 

 The relation C = 2H no longer applies to carbon compounds in 

 general. What is true of carbon and hydrogen is equally true of 

 oxygen, whether as carbonyl- or as hydroxyl-oxygen. No definite or 

 uniform values can be assigned to oxygen such that the molecular 

 volume of a liquid can be a priori determined. The values given by 

 Kopp are simply mean values, but the actual volumes are affected by 

 conditions of which, as yet, we have no very precise knowledge or any 

 certain means of measuring. The values for the other elements are, 

 of course, affected by these considerations. Thus the specific volume 

 of chlorine is obtained on the assumption that the values for carbon 

 and hydrogen are constant. All, then, tends to show that the molecular 

 volume is not the sum of constant atomic volumes. 



Although Kopp's theoretical conclusions hardly admit of the 

 generality which he assumed them to possess, his experimental work 

 remains unassailed and unassailable, a monument to his ingenuity, 

 manipulative skill, his rigid sense of accuracy, and illimitable 

 patience. 



T. E. T. 



Dr. JOHX RAE, LL.D. (Edin.), a traveller in Arctic America, of 

 extraordinary energy and endurance, a keen observer of Nature, and 

 the discoverer of the fate of the Franklin expedition, was born in 

 Orkney in 1813, died in London in 1893, and is buried in the 

 cathedral of St. Magnus at Kirk wall, where a statue is erected to his 

 memory. 



He qualified as a surgeon in Edinburgh, and as such he accom- 

 panied one of the ships of the Hudson's Bay Company, whose service 

 he joined, and then for ten years he resided at Moose Factory. 

 (1) His first journey of pure exploration was a boat voyage along the 

 coast of Hudson's Bay to Repulse Bay, where he wintered, and, in 

 the following year he surveyed a coast line of 700 miles, connecting 

 the surveys of Ross in Boothia with those of Parry at Fury and 

 Heckla Strait. (2) Next he joined the expedition of Sir J. Richard 



b 2 



