A determination, more exact than had been previously obtained, of the relation of the weight of air to the weight of mercury, had furnished a direct value of the coefficient of the barometrical formula which served for the calculation of the heights. I had contributed, in a regular and very assiduous manner, during nearly two years, to the observations which were made day and night with the transit telescope and with the mural quadrant at the Paris Observatory. I had undertaken, in conjunction with M. Bouvard, the observations relating to the verification of the laws of the moon's libration. All the calculations were prepared; it only remained for me to put the numbers into the formulae, when I was, by order of the Bureau of Longitude, obliged to leave Paris for Spain. I had observed various comets, and calculated their orbits. I had, in concert with M. Bouvard, calculated, according to Laplace's formula, the table of refraction which has been published in the _Recueil des Tables_ of the Bureau of Longitude, and in the _Connaissance des Temps_. A research on the velocity of light, made with a prism placed before the object end of the telescope of the mural circle, had proved that the same tables of refraction might serve for the sun and all the stars. Finally, I had just terminated, under very difficult circumstances, the grandest triangulation which had ever been achieved, to prolong the meridian line from France as far as the island of Formentera. M. de Laplace, without denying the importance and utility of these labours and these researches, saw in them nothing more than indications of promise; M. Lagrange then said to him explicitly:-- "Even you, M. de Laplace, when you entered the Academy, had done nothing brilliant; you only gave promise. Your grand discoveries did not come till afterwards." Lagrange was the only man in Europe who could with authority address such an observation to him. M. de Laplace did not reply upon the ground of the personal question, but he added,--"I maintain that it is useful to young savans to hold out the position of member of the Institute as a future recompense, to excite their zeal." "You resemble," replied M. Halle, "the driver of the hackney coach, who, to excite his horses to a gallop, tied a bundle of hay at the end of his carriage pole; the poor horses redoubled their efforts, and the bundle of hay always flew on before them. After all, his plan made them fall off, and soon after brought on their death."