I09 



Jacquelin liad been able to heat starch granules to 300 degrees in 

 water, and then regain them in their original form by simple evapo- 

 ration of the water ; but he should like to see such a granule. 



Examined b>' polarised light the starch granule gave a black 

 •cross, which changed as the prism was rotated, or when a selenite 

 plate was interposed a coloured cross, on a different coloured ground, and 

 it then formed one of the prettiest objects that could be exhibited 

 under the microscope. Starch was obtained by rasping or grinding 

 roots, &c., and then washing the mass upon a sieve ; by which the torn 

 cellular tissue was retained, while the starch passed through with the 

 liquid, and eventually settled down from the latter as a soft white 

 insoluble powder. Starch from the grain might be prepared by mixing 

 the meal with water to a paste and washing on a sieve ; but it was 

 commonly manufactured on a large scale by steeping the material 

 in water for a considerable time, when the lactic acids, always 

 developed under such circumstances from the sugar of the seed, dis- 

 integrated, and in part dissolved the azolized matter, thereby greatly 

 facilitating the mechanical separation of that which remained. A still 

 more easy and successful process had lately been introduced, in which 

 a very dilute solution of caustic soda, containing about 200 grains of 

 alkali to a gallon of liquid, was employed for the same purpose. 



Among the starches which would be exhibited were sago and 

 tapioca, which one saw figured in nearly every work on the microscope, 

 but of which he had great difficulty in .obtaining samples. The 

 articles sold under those names consisted of starches in a partially 

 cooked slate, some of the granules having been converted into a kind 

 of mucilage, which had firmly cemented the remainder into compact 

 masses. But both sago and tapioca had been imported in the raw 

 state, and, judging from the appearance of some of the soluble cocoas, 

 there must be a considerable quantity of sago meal in England some- 

 where. Arrowroot, known as West Indian arrowroot, obtained from 

 the tubers of MaraJtfa Arundinacca, formed the ordinary arrowroot of 

 commerce, the value of which varied so greatly with the amount of 

 care taken in its preparation and the part of the world from which it 

 came, that the higher qualities were quoted at fully three times the 

 value of the lower, although obtained from the same plant. East 

 Indian arrowroot yielded by the Rhizomes of Ctircuma Aiigustifolia 

 and CUtuorrhiza, had a very characteristic appearance and was 



