100 On the Chemical Nature ofEquiseta, or Horsetails. 



The same colour is also observed in many web-footed birds, 

 which cover their eggs when they leave then), and which are 

 moreover careful to look after them ; as swans, geese, ducks, 

 divers, &c. The eggs of certain large birds which nestle in the 

 open air, are even of a muddy white, as is observed in vultures, 

 eagles, and storks. 



Among the party-coloured eggs, there are distinguished those 

 which have a white ground, and those whose ground is of some 

 other colour than white. The eggs which have a white ground 

 are those of the golden oriole, the long-tailed titmouse, the nut- 

 hatch, creeper, chimney-swallow, &c. Most of their eggs are 

 concealed in nests that are well covered. The party-coloured 

 eggs, whose ground is not white, at least not pure white, are 

 those of the lark, titlark, some wagtails and buntings ; those of 

 crows, shrikes, thrushes, quails, and most of the singing birds, 

 in which the colour of the interior of the nest accords with that 

 of the eggs. 



O71 the Chemical Nature of Equiseta, w Horsetails. 



JliVERY body knows that the Equiseta or Horsetails, which are 

 rough plants covered with asperities, are much employed for po- 

 lishing wood, metals, &c., and for scouring culinary utensils. 

 But it is probably less known that these plants are not less re- 

 markable in a scientific point of view than with reference to the 

 arts. Their singular structure, which completely separates them 

 from all other vegetables, has given rise to interesting researches 

 on the part of botanists, among which we must assign the first 

 rank to those which M. Vaucher has published in his Monograph 

 of the Equisetaceae. Natural philosophers have also made some 

 curious observations on these plants, such as the examination of 

 the remarkable optical properties possessed by the small crystals 

 which the microscope discovers in their dried tissue. 



It was therefore to be desired, that chemists should also ex- 

 amine the equiseta, and make known to us the elements which 

 enter into their composition. Accordingly, M. Braconnet has 

 engaged in this kind of investigation ; and it is from a memoir 



