48 Journal of the Mitchell Society. [ June 
a profile for 224 feet in depth, exactly the same as the Qua- 
ker bridge design for the same depth. 
Engineering News for June 30, 1888, January 12, 1893, and 
May 9, 1907, is referred to for the destructive action of ice 
on ponds, lakes, and rivers, due to the expansion from an 
increase of temperature during the day. At night, contrac- 
tion causes cracks to form, often several inches wide, which 
are filled up with new ice and thus the effect, from day to 
day is cumulative and very destructive as far north as Can- 
ada and in the Northern States. As yet, the action of ice on 
high dams has not received much attention. 
For earthquake action on houses, Milne is referred to; also 
a personal experience of the author in Charleston, S. C., is 
recited. It was pointed out, however, that dams being built 
into the sides of the valley at their ends, were not so free to 
move at their tops as houses. 
A brief description and analysis of the failure of the Habra 
dam concludes the paper. 
13. Three Little Known Species of North Carolina Fungi, 
J. G. Hall, of the North Carolina Experiment Station. 
14. A New Form of Achlya, W. C. Coker, of the University 
of North Carolina. 
During the fall of 1906 an Achlya was found at Chapel 
Hill, N. C., which agrees with Achlya racemosa, var. stel- 
ligera Cornu, in many respects, but different from it in having 
the autheridum cut off immediately below the oogonium, and 
the fertilizing tube arising from the division wall and enter- 
ing the oogonium from below, as in Saprolegnia hypogyna 
Pringsheim. Such an origin for the fertilizing tube is new 
for the genus Achlya, and is not known elsewhere except in 
Saprolegnia hypogyna. 
15. Notes upon the Preparation of the Silicate Medium for 
the Cultivation of Bacteria, J. C. Temple, N. C. Agri- 
cultural Experiment Station. 
