IOWA ACADEMY OP SCIENCES. 
143 
The critical temperature can be calculated from measure- 
ments of surface tension, leaving only two series of data which 
may be correlated by the method of comparison, since both the 
tenacity of the solid and the surface tension in the liquid state 
can be found for some elements. 
Unfortunately I have not been able to collect sufficient data 
to draw the curve even approximately, but an inspection of the 
elements on Meyer’s curve shows that the curve in space will 
approximate a spiral, of which Meyer’s curve is a projection. 
For example: The volatile element flourine and the metal 
magnesium will stand near the top and bottom of the curve 
respectively, and in general the elements on the rising branch 
will be high, and those on the falling branch of Meyer’s curve 
low, wdth respect to the third co-ordinate. Melting points, 
boiling points, hardness, and other related -properties of the 
elements are likely to be much more clearly represented on this 
curve than they are by either Meyer's or Mendeleeff’s system. 
CERTAIN MINERALS OF WEBSTER COUNTY, IOWA. 
BY ARTHUR C. SPENCER. 
Within the limits of Webster county are found a number of 
interesting minerals. The following notes are descriptive of a 
few of them. 
Quartz. In the vicinity of Fort Dodge the sandy deposits 
overlying the gypsum are full of rough calcareous concretions 
of irregular shape. These formations are never hollow like 
geodes, but like them consist largely of quartz crystals. Cal- 
cite showing little or no crystalline character surrounds and 
incloses perfect crystals of doubly terminated quartz. These 
small crystals rarely exceed 3 mm. in length. They show only 
the simple forms of the unit prism and the unit rhombohedron. 
Its intimate association with calcite indicates that the quartz 
was without doubt deposited by circulating carbonate or alka- 
line waters. 
Pyrite. Though of very frequent occurrence throughout 
the coal measures of Webster county no good crystals have 
