M. Caven toil's Chemical Researches on Starch, Sfc. 283 



In the lunar method the uncertainty arising from this cause 

 would have been simply the sum of two of these numbers, one 

 from each table; namely, 4-' 17", or 3' 20", according as the 

 ship time might be found from the altitude of the sun or the 

 moon. 



If in this example the latitude and altitudes could be sup- 

 posed uncertain only a quarter of a minute, even then would 

 the longitude be uncertain by nearly a whole degree ; an un- 

 certainty so much greater than could possibly exist in the 

 result as determined by a Lunar Observation, if taken by a per- 

 son of even the most moderate skill in observing, — that simple 

 as the method is in theory, and easy as it would appear in 

 practice, it cannot, as I think, be adopted at sea with any pro- 

 spect of advantage. 



Mr. Lynn's method being liable to exactly the same prac- 

 tical objections as Mr. Yarrow's, any additional remarks upon 

 it would be superfluous. 



I am, sir, your obedient servant, 



Greenwich Hospital, Oct. 14, 1826. E. RlDDLE. 



XLIII. Chemical Researches on Starch, and the different amyla- 

 ceous Substances qf Commerce. By M. J. B. Caventou.* 



[Read at the Royal Academy qf Medicine qf Paris.) 



1V/|"ORE than eight years since, I undertook an investiga- 

 4 - tion of the various amylaceous substances which are ob- 

 jects of commerce, in which they are designated by the names 

 of salep, sago, tapioca, and arrow-root. I gave at that period 

 an account of my first researches to the Society of Pharmacy, 

 and was disinclined to publish them, because several of my 

 results did not appear to me to present the general cha- 

 racters which I sought. I was then not aware of the al- 

 terations and adulterations which these substances are made 

 to undergo in commerce. Besides, I intended to attempt 

 some new researches on starch or fecula, whose chemical 

 characters, under certain circumstances, did not appear to me 

 to be sufficiently well established, and even seemed quite un- 

 known. 



In 1822 I attempted some new experiments ; and found some 

 rather interesting facts, which I entered in my memorandum- 

 book, without making any other use of them, because I always 

 hoped to be able to complete the train of research which I 

 had in view. Circumstances had in some decree made me 



* From the Annates de Chime et de Physique, torn. xxxi. p. 337- 



2 N 2 forget 



