170 Proceedings of the Royal Academy of Paris. 



of nutriment, when the fact may turn out to be that the gelatine is 

 not nutritious, their condition is rendered more deplorable than 

 before. In conclusion, he said that he rendered full justice to the 

 active and pure philanthropy of M. D'Arcet, which had induced him 

 to make the greatest sacrifices both of time and money, in order to 

 bring the gelatinous system to perfection. 



Mirage by Suspensio?i. On the 20th of June, a letter was read 

 from M. Rozet, stating that he had frequently remarked this atmos- 

 pheric phenomenon in the neighbourhood of Algiers, and particu- 

 larly on the 27th of June, 1830, when about ten o'clock in the morn- 

 ing, at which time the sky was perfectly clear, and the thermometer 

 at 21 (Reaumur), he distinctly saw, when looking at the line of 

 battle formed in the camp at Staonelli, two images of all the objects, 

 the mirage being about half as strongly marked as the real image, 

 but still perfectly distinguishable and elevated above the object about 

 one-fourth of its height, deviating a little laterally. On the Algerine 

 tents, surmounted with tin spheres, with a crescent on the top, the 

 image of a second crescent forming a tangent to the first, was dis- 

 tinctly visible, so that, at first sight, it appeared as if there were two 

 crescents to each tent. When the images are reversed, they are 

 rarely clear, and have always a perceptible movement of undulation. 



Climate of Algiers. The same letter stated, that whenever the 

 south wind blows in the neighbourhood of Algiers, the temperature is 

 raised from 5 to 10 C. (41 to 50 F.) On the 17th of September the 

 thermometer stood at 39(103F.) in the shade. Those who happened 

 to be affected by drinking at that time, suffered severely, falling down 

 insensible. This wind rarely lasts twenty-four hours, and occasions 

 as much inconvenience to the natives as to the French. Storms are 

 not frequent at Algiers, but when they occur they are of great 

 violence. On the 8th of May last, the whole horizon was a sheet of 

 flame ; a strong white light rested for half an hour on the extremities 

 of the flag-staffs of the forts of Algiers and its vicinity, and the officers, 

 who were walking bareheaded on the terrace, felt their hair stand on 

 end, and perceived a luminous star at the extremity of each ; the 

 same species of star was observed on the ends of the fingers 

 when held upright in the air, but disappeared when held downwards. 

 During these storms every one is affected with great lassitude, parti- 

 cularly in the legs, and experiences strong nervous agitation. 



New Chart. At the same meeting M. Coplin presented a topo- 

 graphical chart of the islands of Perouse, in which, by a new plan of 

 drawing, in imitation of relief, he has succeeded in so well availing 

 himself of the process of shading, that not only the geological consti- 

 tution, and the direction of the declivities, but also the variations in 

 the surface of the different mountains are distinctly exhibited to 

 the eye. 



