In Memoriam . 
437 
In the line of petrographic genesis Professor Irving made two very- 
notable contributions, first, the demonstration of the prevalence and 
importance of the secondary growth of certain fragmental constituents 
of clastic rocks and the crystallographic co-ordination of the additions 
with the nuclear particles. The existence of such a second growth in 
quartz grains was an earlier discovery of others but was hit upon by 
him independently. Jointly with his co-laborer, Professor Van Hise, he 
demonstrated a similar second growth of hornblende and other min¬ 
erals and showed that such rebuilding was a prevalent process, consti¬ 
tuting an important element in those changes heretofore designated 
metamorphic, thereby contributing an important factor in the elucida¬ 
tion of that mysterious process. 
Perhaps the most important single determination by Professor Irving, 
and one of his latest, was the demonstration of the origin of the iron 
ores of the Lake Superior region. By a series of admirable investiga¬ 
tions he traced step by step the transformation of the ores from original 
earthy carbonates of iron to their present forms, and made it altogether 
clear that they were primarily deposited as sediments in a manner 
closely similar to that of the iron ores of the Coal Measures. This dis¬ 
covery has given added significance to the association of these ores 
with carbonaceous shales, and has led to the recognition of the iron¬ 
bearing series as marking in some sense a pre-Cambrian carboniferous 
period. 
The characteristics of Professor Irving as a scientific investigator 
and writer are too well known to the readers of this magazine to need 
analysis here. Personally, to those who came within the circle of his 
intimate acquaintance, he possessed rare charms of character. Sincere, 
frank, conscientious in the highest degree, he was a warm and true 
friend. Possessed of a rollicking brusque humor, his intercourse was 
marked by a freshness that was a source of constant enjoyment and 
attraction to his intimate associates. No phrase better expresses it 
than picturesqueness. Modest and retiring, the number of his close 
friends was not large but their attachment to him was strong. The full 
strength of these attachments has only been realized in their breaking. 
He leaves a wife, a daughter and two sons. The artistic skill of Mrs. 
Irving appears in some of the sketches and particularly in many of the 
microscopic illustrations of her husband’s works. 
