Accidental and Complementary Colours. 217 



in my next paper, which will appear in the ensuing number 

 of the Records, state, first, the various means by which 

 coloured shadows can be procured ; and, secondly, the 

 application of my theory to their explanation. 



Salisbury, November, 1835. 



Article IX. 



The Atmosphere in relation to Malaria. 



That diseases, possessing a variety of types, originate from 

 the existence of matter in the air we breathe, has been be- 

 lieved from the remotest ages. This is most distinctly true 

 in woody or marshy countries, when attempts at colonization 

 are first made. The fine town of Amaga, in Antioquia, 

 Boussingault, {Ann. de Chim., Ivii. 150,) tells us, was 

 founded in a forest. For six years, the population remained 

 stationary ; but, at last the roots and branches of the trees, 

 having been completely removed in the lapse of a short 

 time, the place became gradually more healthy, and it is 

 now one of the most important little towns in the province. 

 Panama, which was covered with wood, when the Spaniards 

 first settled in it, possessed a deadly climate ; but, at the 

 present day, with the exception of the marshes of Chagres, 

 the Isthmus is as healthy as any part of the coast of the 

 Pacific in these latitudes. The influence of marshes in 

 producing disease seems to be increased, when the water 

 of the ocean becomes mingled with fresh water. Thus, 

 Via Reggio, at the foot of the Appenines, in 1733, was so 

 unhealthy, that the population did not exceed 330 inhabi- 

 tants. But, in 1743, the sea-water was shut out from the 

 lakes in the interior; and the consequence has been, that 

 the town has become so salubrious, that the population, in 

 1823, amounted to 4000 souls. The town of Caitia, near 

 Venezuela, from the same cause, is so unhealthy, that the 

 negroes, when unable to pay their debts, make use of it as 

 a sanctuary, well assured that their creditors will not have 

 the temerity to pursue them thither. In such situations 

 as we have described, where the climate is characterized 

 by a high temperature and moist soil, the diseases of most 



