USE OF METEOROLOGICAL OBSERVATIONS TO NAVlGATORd# ^Q 



of hidrogen gas must take place in the hold ; but thifl action 

 is irwcreased in consequence of the salts with which the water 

 is impregnated, and the high temperature generally prevail- 

 ing in the hold : and this hidrogen gas receives from various 

 vegetable or animal substances m a state of decomposition, 

 in the place where it is evolved, those noxious qualities, 

 and that sulphuretted smell, of which I have several times 

 spoken. 



It is easy however, in a ship in good condition, to prevent, Remedy ft* 

 if not the formation of this gas, at least its injurious effects. ^^"* 

 This is to be accomplished chiefly by frequently pumping 

 the ship out dry, and then throwing in a large quantity of 

 water, both to wash out and carry off all the substances in a 

 state of decomposition, and to cool the hold. But in ships 

 where these little attentions are neglected, the black oxide 

 of iron, which is formed in abundance by the decomposition 

 of the ballast, mixing with the remains of vegetable and even 

 animal substances in a state of fermentation, produces a kind 

 of stinkmg black mud, the exhalations of which have frCf 

 quently produced fatal disicases on board ships. 



Hence it is easy to perceive, how much this part of the Necessity of 



ship should be an object of attention to the officers and sur- a,"*"*'®" ** 



, . . tLe hold, 



geons. From it arise most of those noxious gasses, and of- 

 fensive smells, that render living on shipboard so unpleasant. 

 The thermometer and hygrometer constantly afforded me 

 valuable data respecting the state of this place with regard 

 to its salubrity; the evolution of gas, and consequently the 

 decomposition of water and of the animal or vegetable sub- 

 stances, being pretty generally in the ratio of the tempera- 

 ture and moisture combined : their use therefore cannot be 

 too sedulously recommended. The same may be said of the 

 preventive means I have mentioned, to which must be adde4 

 above all the apparatus for oximuriatic gas; as here in par-? 

 ticular it may be employed with the greatest success, and 

 without any inconvenience. 



The observations 1 have just mentioned were nearly the j^g author 

 last of the kind I could make. Notwithstanding the request obliged to 

 of the captain himself, I was obliged to sacrifice them to pri- *^ej^yations° 

 vate considerations, which it would be useless to mention 

 iiere. So true it is, that to have both the means and the de- 

 sire 



