Scientific Intelligence — Meteorology. 181 



the magnetic needles all over the world, as exhibited at the respec- 

 tive Observatories ; and he explains the apparent anomalies which 

 occur at St Helena and Singapore on the hypothesis induced from 

 the whole of the phenomena. The lecturer, in closing, stated that 

 the explanation was to be received as conjectural, although, at pre- 

 sent, as sufficiently satisfying the theory. — AthentBum, No. 1206, 

 p. 1282. 



4. On a Cloud of Dust which obscured the Sun for two days in 

 Russia, on the 29th and ^Oth April 1840, during a clear sky and 

 quiet weather. — This powder was furnished Ehrenberg by M. Eich- 

 wald. Microscopic examination brought to light forty-nine animal 

 forms, soft portions of plants, a few crystals, a morpholite, and some 

 sand. This powder is distinguished from that of the trade winds by 

 some prominent forms. Ehrenberg believes that there is reason 

 for concluding that this meteoric powder is neither a terrestrial 

 powder nor simple volcanic cinders. 



5. Shower of Aerolites. — Extract of a letter from Mr Richard- 

 son, dated Jerbah, 25th January 1850 : — 



** I will trouble you by the mention of the astronomic phenome- 

 non which terrified or arrested the attention of the inhabitants of 

 the whole of this coast some two months ago. This was the fall 

 of a shower of aerolites, with a brilliant stream of light accom- 

 panying them, and which extended from Tunis to Tripoli, some of 

 the stones falling in the latter city. 



" The alarm was very great in Tunis, and several Jews and Moors 

 instinctively fled to the British Consulate, as the common refuge 

 i'rom every kind of evil and danger. 



" The fall of these aerolites was followed by the severest or cold- 

 est winter which the inhabitants of Tunis and Tripoli have experi- 

 enced for many years." 



6. Destruction of Forests in Madeira. — The progressive destruc- 

 tion of the forests, since the first discovery of the island of Madeira, 

 has very materially modified the climate, by making it less humid. 

 The smooth surfaces of leaves of the trees of the laurel tribe, 

 cool rapidly by radiation, when the sky is clear ; and the dew being 

 consequently, deposited profusely upon them, they collect and distil, 

 as it were, water in great abundance from the atmosphere. When 

 the island was first discovered, and for many years afterwards, while 

 the northern mountains were covered with evergreen trees, the river 

 Socorridos — the most considerable in Madeira — which runs through 

 the Curral, was found to be sufficiently deep to float timber to the 

 sea, which it enters near Camea dos Lobos. It is now reduced, 

 when not suddenly flooded, to a small stream, almost lost in the 

 loose rocks which occupy its channel. It would appear that the 

 attention of the settlers was called, at a very early period, to the 

 injurious effects produced by the rapid diminution of the forests in 

 a country ; where, from the dry and porous character of the soil, and 

 the warmth of the climate, moisture becomes the great principle of 



