The siliceous residue from the scum was examined by Dr. S. W. Williston. It consists mostly of diatoms. He recognized
- Navicula— 2 species
- Nitzschia— 2 species
- Asteronella— 1 species.
All three genera are found both in fresh and salt or brackish water.
The green material consists essentially of Oscillaria and Confervæ. If the scum is allowed to stand for a short time a very strong sulphuretted odor is developed, strangely suggestive of salt water marshes or mud flats; and indeed the same odor is noticed in the vicinity of the spring. No characteristic salt water organisms, that should occasion this peculiar odor have, however, yet been observed here. A more extended and special study of the organic life of these interior salt water marshes and springs would be of great interest.
On Pascal’s Limaçon
and the Cardioid.
BY H. C. RIGGS.
The inverse of a conic with respect to a focus is a curve called Pascal’s Limaçon. From the polar equation of a conic, the focus being the pole, it is evident that the polar equation of the limaçon may be written in the form: