388 Scientific Intelligence. 
molten iron must undergo a rapid expansion in the moment of its 
solidification. The extent of this expansion is, however, less than 
that of the subsequent contraction in cooling, so that the cold iron 
is again denser than the molten iron. 
The error of Mr. Mallet and of many preceding observers con- 
sists in this: Their observation, that the solid metal floats on the 
molten metal refers to the former when heated, while their determi- 
? 
does not float, and the heated metal which does float has undoubt- 
edly a smaller specific gravity. There is certainly nothing either 
incongruous or wonderful in all this, and nothing that would 
require or justify the assumption of a “repellent force.” None o 
Mr. Mallet’s experiments, as far as they are mentioned in the 
“Journal,” prove anything against the temporary expansion of 
tions I made on this point in foundries verify it. 
Washington University, St. Louis, Mo., September 21st, 1874, 
Il. GroLtoagy anp Natura History. 
‘ GABB. 
Mey following letter was recently received from Mr. Gabb, who 
ports, maps, etc. ‘The close of the survey, in fact the last half, 
found me the only representative of the original corps. Not only 
first assistants, but in some cases two relays of substi- 
tutes, gave out and retired, with health seriously injured. cd 
man, now a year in a healthy climate and in the doctor’s hands, 
is not well yet. Fortunately, I lost no lives, and, so far as I my- 
self am concerned, neither my life nor my spleen is injured, and 
except being a little lighter in weight I am as good as new, and 
ready to go into the field again as soon as my report is finished 
and my money paid ! 
We were about four months away on my last journey, and 
while our hardships were neither few nor trivial, our scientific re- 
sults were satisfactory. 
reached the summit of Pico Blanco June 13, and spent three 
hours on the summit. ithout having at hand the tables for 
going into the calculations for corrections, etc., the barometric re- 
Sults are approximately 10,200 feet. This is 1,500 feet lower than 
