39S Meteorological Olservtitlom 



Meteorological Observations made at Cambridge, from April 

 29, to May 11, 1813. 



April ^g. — Rainy morning, and cold, cloudy, and windy 

 aFternoon ; with cold northerly gales. The thenuomtter 

 at Jl P.M. was 42°. 



April 20. — Cold, rainy, and windy morning ; it became 

 warmer in the evening, and held up; but the night was 

 dark and calm ; and ihermomeler at II P.M. 44°. 



May 1. — Cloudy, with a good deal of small rain. Ther- 

 mometer at midnight 46". Wind easterly. 



May 2. — Clouds and threatening rain in the morning j 

 the day cleared, and was calm and warm, with large con- 

 fluent cumuli; cirrostratus and red haze in the west in the 

 evening. Thermometer at 1 1 P.M. 48°. In the day were 

 occasional and gentle gales of wind from ihe north*. 



May 3. — Overcast early, afterwards clear. About ten 

 o'clock in' the morning,^ looking up I noticed the following 

 phaenomena : large beds of cirrus of flimsy but fibrous 

 structure, changed into larger and more discrrminativecirro- 

 stratous lines, and afterwards into cirrocumvlus whose im- 

 leculce were small ragged pendulous and confluent aggre- 

 gates, which continually changed their forms ; v/hile others 

 were added at one extremity of the bed, by an apparent de- 

 position of mist which separated into rows, and lastly be- 

 came cirrocumuli by subdivision : such phoenomena ap- 

 pearing and disappearing continued above, while cumjili 

 sailed along below with motions not uniform either as to 

 direction or velocity. Through the day cumuli increased 

 in number, and cirrus appeared above; in the evening the 

 clouds were confused and in different altitudes with a hazy 

 moon. Thermometer 2 P.M. 66", at 11 P.M. 51°. Wind 

 below easterly. Showers came on in the night. 



May 4, — Warm morning with gentle showers, and 

 nearly calm air in variable currents. A thunder-storm oc- 

 curred about two P.M. the thermometer just after it was 

 63". After one of the flashes of lishtning the rain came 

 dovjm with redoubled violence, mixed with hail. This 

 augmentation of the strength of the shower often succeeds 

 a discharge of lightning f. Thermometer at midnight 5o°. 



* A thick and sudden fog of short duration happened near London this 

 day at about one o'clock. At Cambridge there was only a niibtiiiess in the 

 middle of the day. * 



f In the formation of thunder-storms, I have noticed that where the rain 

 actiia!ly begins to form and descend, the intensity of the blackness is not no 

 great a; where the cunndiislratits is only going- into a stale of jinnbtts. If 

 tliert'lore the density is increased in the formation of drops of water, the 

 tiatiijjcjs must depend on some other peculiarity of structure. 



May 



