in relation to Disease. 49 



have yet been made, and a careful comparison of these with the 

 physical properties of the winds in question, which future re- 

 search may also better determine. 



Whatever the natural causes which render some of our east- 

 erly winds thus peculiar, that from the south-east may certainly 

 be considered to have direct connexion with the Sirocco, as it 

 sweeps with greater or less intensity over the southern half of 

 Europe. This very singular atmospheric current, which, on its 

 more distant border, has probable relation to the Simoom and 

 Harmattan, the hot winds of African desert, — and passes over 

 the Mediterranean Sea under the names of the Levant wind 

 and Sirocco, — reaches England on the opposite side, — its pe- 

 culiar qualities much mitigated, yet still shewing the same 

 origin in its general direction, in its hygrometrical conditions, 

 and in what I believe to be its electrical influence on animal 

 life. No sufficient explanation has yet been given of these pe- 

 culiarities, nor are they perhaps definite enough as facts to 

 warrant much theory on the subject. I cannot doubt, however, 

 from my own observations, that the electrical state of these 

 great atmospheric streams, whencesoever derived, is that to 

 which their effects are mainly due. I have witnessed in dif- 

 ferent parts of the Mediterranean such singular and repeated 

 proofs of this as to give assurance of the general fact, though 

 there are yet wanting the exact determinations required to fix 

 its place in the history of physical phenomena. 



Our knowledge of atmospheric electricity is, in truth, still 

 in its infancy. What was written on the subject by Mr Luke 

 Howard and others, at a comparatively early period in the 

 history of the science, is still an authority to which little has 

 been added, in proportion to its progress in other parts. The 

 causes of production, distribution, and change ; — its relation 

 to that electricity which circulates in magnetic currents, or 

 otherwise appertains to the earth, or may possibly exist in space 

 beyond the atmosphere ; — its connexion with atmospheric heat, 

 moisture, or weight ; with the formation of clouds ; and tho 

 phenomena of wind, thunder-storms, and rain ; — and, above 

 all, the relation of its positive and negative states — each one 

 of these conditions is still largely open to inquiry. The latter 

 especially, which has most assured and closest relation to all 



VOL. XXIX. NO. LVII.— JULY 1840. D 



