PROCEEDINGS OF THE POLYTECHXIC ASSOCIATION. 595 



tliread. The common nettle (nrtica droica) may be advanta- 

 geously manufactured into cloth: also the white leaved nettle 

 (urtica nivea), the hemp-leaved nettle (urtica cannabina), the 

 swallowwort (asclepias syreaca), are good textile plants. There 

 are other common plants that yield fibres sufficiently strong for 

 thread, as the esparto-rush (stipa tenacissima), the common 

 broom (cytisus scoparia), the Spanish broom (spartium junceum), 

 different species of the aloe, and sundry plants of the lily tribe. 

 Our southern regions abound in plants that possess a fibrous 

 structure, which renders them capable of being employed in the 

 manufacture of thread, cordage and cloth. 



Wool, from its filamentous texture and elasticity, has many ad- 

 vantages over all other materials used for clothing, it possesses 

 a felting property that enables the manufacturer to render it ex- 

 ceedingly compact, or so thin as to rival cotton goods ; it is a 

 much better non-conductor of heat than cotton or linen, and 

 when worn next the skin prevents the heat of our bodies from 

 escaping, and consequently prevents us from sudden external 

 changes of temperature. Its rough surface causes cutaneous ex- 

 halations from the skin to a greater degree than any other known 

 TQaterial, and will alwa^^s be found serviceable in preserving any 

 who may be exposed to epidemic influences, malaria, &c. And I 

 believe that those persons who may, from necessity or otherwise, 

 be compelled to reside in a fever and ague district, will be pre- 

 served from its effects by wearing flannel next the skin. On the 

 Pontine marshes, and Roman plains, where epidemics of all kinds 

 abound, I noticed that the shepherds were invariably, during the 

 warmest days in summer, clothed in sheepskins, and I never saw 

 more healthy looking men than they were, except, perhaps, the 

 Catholic priests. 



One hundred parts of merino fleece contains : 



Fat matters, capable of being dissolved by Avashing 33.00 



Earthy substances 26.00 



Fat matters _ 10.00 



Clean wool 31.00 



100.00 



The influence of temperature on the growth of wool is very 

 great. Sheep grown in a hot climate yield coarse wool, and those 

 in a cold climate, fine. The staple of wool may be increased in 



