3.  Coast hills inclosed sea sediment, now rock containing fossil leaves.

4.  Wash from this sediment, carried with care, formed layers of sandstone, up to ceiling.

5.  This ceiling was covered with elaborate inscriptions.

6.  The inscription sent you was a near neighbor to cave.

7.  Another representing a saurian reptile on large granite bowlder is also a neighbor (a glacial dropping).

8.  Old river emptying into Lake Managua reveals fossil bones; moraines east of it are found.

From these data we see the glacial action was prior to the sedimentary rock here, and had spent its force when elevation of coast range occurred.  No nearer estimate is possible.

As the fossil horse occurs here, our mounted man may have domesticated him, and afterward slaughtered for food like the modern Frenchman.  Unfortunately Prof.  Cope did not find a similar inscription.

EARL FLINT. 
Rivas, Nicaragua, October 27, 1891.

* * * * *

FURTHER RESEARCHES UPON THE ELEMENT FLUORINE.

By A.E.  TUTTON.

Since the publication by M. Moissan of his celebrated paper in the Annales de Chimie et de Physique for December, 1887, describing the manner in which he had succeeded in isolating this remarkable gaseous element, a considerable amount of additional information has been acquired concerning the chemical behavior of fluorine, and important additions and improvements have been introduced in the apparatus employed for preparing and experimenting with the gas.  M. Moissan now gathers together the results of these subsequent researches—­some of which have been published by him from time to time as contributions to various French scientific journals, while others have not hitherto been made known—­and publishes them in a long but most interesting paper in the October number of the Annales de Chimie et de Physique. Inasmuch as the experiments described are of so extraordinary a nature, owing to the intense chemical activity of fluorine, and are so important as filling a long existing vacancy in our chemical literature, readers of Nature will doubtless be interested in a brief account of them.

IMPROVED APPARATUS FOR PREPARING FLUORINE.

In his paper of 1887, the main outlines of which were given in Nature at the time (1887, vol. xxxvii., p. 179), M. Moissan showed that pure hydrofluoric acid readily dissolves the double fluoride of potassium and hydrogen, and that the liquid thus obtained is a good conductor of electricity, rendering electrolysis possible.  It will be remembered that, by passing a strong current of electricity through this liquid contained in a platinum apparatus, free gaseous fluorine was obtained at the positive pole and hydrogen at the negative pole.  The amount of hydrofluoric acid