The SPANISH ACADEMY OF SCIENCES have announced the following subject for competition: "An experimental investigation and explanation of the theory of nitrification, the causes which most influence the production of this phenomenon, and the means most conducive in Spain to natural nitrification." The prize, to be awarded in May 1851, is to be a gold medal and 6000 copper reals--about seventy pounds sterling; and a second similar medal will be given to the second best paper. The papers, written in Spanish or Latin, are to be sent in before the 1st May, with, as usual, the author's name under seal. * * * * * IMPROVEMENTS IN THE TELEGRAPH.--The _Presse_ gives some account of experiments made at the house of M. de Girardin, in Paris, with a new telegraphic dictionary, the invention of M. Gonon. Dispatches in French, English, Portuguese, Russian, and Latin, including proper names of men and places, and also figures, were transmitted and translated, says this account, with a rapidity and fidelity alike marvelous, by an officer who knew nothing of any one of the languages used except his own. Dots, commas, accents, and breaks were all in their places. This dictionary of M. Gonon is applicable alike to electric and aerial telegraphy, to transmissions by night and by day, to maritime and to military telegraphing. The same paper speaks of the great interest excited in the European capitals by the approaching experiment of submarine telegraphic communication between England and France. The wires, it says, on the English side are deposited and ready for laying down. It is probable that in a very few days the experiment will be complete. * * * * * AUTHORS AND BOOKS. * * * * *