76 ROYAL SOCIETY OF CANADA 



There is one circumstance which lessens the importance of these 

 observations as to the temperature ; it is not established that the ice 

 at the bottom of the river on the 16th February was formed on that 

 day, and these ices might again cover the bed of the river for many 

 days afterwards. 



The second series of the observations of M. Hugi were made in 

 the month of February, 1829. 



On the 11th of this month, the Aar near Soleure was quite free 

 from ice. For many days the temperature of the atmosphere was 

 from 4-4° to +6° centigr. During the night of the llth-12th, it 

 suddenly fell to — 14° centigr. In the 12th at sunrise, the river 

 began to exhibit numerous floating pieces of ice. "We must by no 

 means omit to add, that the water, either near the banks, or in the 

 shady places where it was perfectly calm, as yet bore no trace of con- 

 gelation on its surface. It, therefore could not be said that the float- 

 ing masses were detached from the banks. It would have been as 

 Tmfounded to have supposed that they had proceeded from any large 

 sheet of ice situated farther up the river, as at Altrey, a league and 

 8 half above Soleure, the river hardly exhibited any ice. Besides, 

 flakes of ice commenced soon to rise up above the bridge, in the place 

 where they had been seen in 1827. Towards mid-day, islands of ice 

 were seen forming in the centre of the river. On the 13th February 

 these were 23 in number. The largest was upwards of 200 feet in 

 diameter. They were surrounded with open water, resisted a current 

 which almost ran at a rate of 200 feet in a minute, and extended 

 over a space of one-eighth of a league. M. Hugi visited them in a 

 small boat. He landed, examined them in every direction, and dis- 

 covered that there was a layer of compact ice on their surface of 5 

 or 10 centimetres in thickness, resting on a mass having the shape of 

 a cone reversed, of a vertical height of 3 or 4 metres, and fixed to 

 the bottom of the bed ' of the river. These cones consisted of half- 

 melted ice, gelatinous, and very like the spawn of a frog. It was softer 

 at the bottom than at the top, and was easily pierced in all directions 

 with poles. Exposed to the open air, the substance of the cones 

 became quickly granulated like the ice that is formed at the bottom of 

 rivers. 



When these observations were being made, the temperature of the 

 air, at 9 mietres above the Aar, was, — 11°. 2 centigr.; at 1™.3, — 9°.4, 

 That of the water, at 5 centimetres deep, 0°.0; at 1™.8, + 1°.0; at 

 0"--.5 from the bottom, +1°.5; at the bottom, 4-2°.4; at 1™. in the 

 ground, +8°.0. 



These determinations of the temperature of the water were obtained 

 in a part of the river which had no ice at the bottona. 



