56 On the Rarer Plants of' North America. 



England to South Carolina, by using the dry deal of that coun- 

 try, the steam is got up in eleven or twelve minutes. 



I may mention, that much depends upon the situation the 

 engine stands in, so as to catch a current of air. Many other 

 reasons may be given ; for instance, a new boiler will get up the 

 steam in a shorter period than an old one. Moreover, much de- 

 pends likewise on the nature of the water ; the water we use has 

 lime in it, which crusts the outsides of the tubes rather thicker 

 than an egg-shell ; it breaks off and rests in the bottom of the 

 fire-box ; it has to be cleaned out by a force-pump every four- 

 teen days ; it will in that time be six inches thick. 



At the Leaster Railway the water was so bad, that the tubes 

 got a strong store tube on the outside ; and had they not got bet- 

 ter water, they must have given up locomotive engines. 



Account of some of the Rarer Plants observed during an Ex- 

 cursion in the United States and the Canadas in 1834. 

 Communicated by Mr James Macnab.* 



Few countries can afford a greater treat to the lover of botany 

 than North America. Its vast extent of diversified surface, and 

 the extremes of climate, cause a peculiarly interesting series in its 

 humbler vegetable productions, which are spontaneously scat- 

 tered throughout its woods and swamps, its hills and river-sides, 

 its pine barrens and rich prairies, in a manner harmonizing well 

 with the surrounding scenery. In spring great portions of the 

 country are covered with the blossoms of interesting dwarf- 

 flowering plants; and as the season advances, more luxuriant 

 herbs take their place ; these are again succeeded in the autum- 

 nal months by numerous species of Compositae, forming at that 

 period the greatest bulk of the herbaceous vegetation of these 

 regions. Through vast tracts of country, where the surface has 

 not yet been disturbed, the distribution of the native plants is re- 

 markable ; many of them seem very irregularly scattered and oc- 

 cupy mere spots at one place, while others are extended over 

 a great extent of surface in dense masses, one species being 



* Jleju] before the Wernerian Natural History Society, 25th April 1835, 



