VOL. XXXVIII.] PHILOSOPHICAL TRANSACTIONS. 66Q 



On these experiments, the editor of the Transactions remarks, that all the 

 differences attending them may he reconciled by reflecting, that ambergris is a 

 substance which contains various foreign admixtures. Hence different speci- 

 mens of ambergris contain different quantities of the acid salt. Thus in one of 

 Mr. Godfrey's experiments, the phlegm had a subacid taste, clearly indicating 

 the presence of that salt, and in another experiment the phlegm tasted like a 

 neutral salt ; whilst the specimen examined by Dr. Neuman yielded a much 

 larger quantity of this salt. He further remarks that the more the salt is 

 enveloped in the oil, the more difficult its separation. Besides, Dr. N. in one 

 of his letters to Dr. Sloane, declares that he never meant it to be understood 

 that he supposed ambergris to be the same as amber (succinum), but merely that 

 it was a bitumen very much allied to amber. With regard to the acid volatile 

 salt, of which he obtained a grain or two in his experiment, he could not (he 

 says) be deceived as to the nature of it: for it was soluble in water like any 

 other salt; it reddened syrup of violets like other acids; and it rose in distilla- 

 tion, a proof that it was volatile. 



j4>i Account of Mr. T. Godfrey s Improvemenl of Davis's Quadrant, transferred 

 to ike Mariner s-Boiv. Communicated hi/ Mr. J. Logan. N° 435, p. 441. 

 Thomas Godfrey, having under the greatest disadvantages, made himself 

 master of the principles of astronomy and optics, as well as other parts of 

 mathematical science, applied his thoughts to consider the instruments used in 

 navigation. He saw that on the knowledge of the latitude and longitude of the 

 place a ship is in, the lives of thousands of useful subjects, as well as valuable 

 cargoes, continually depend ; that for finding the first of these, certain and easy 

 methods are furnished by nature, if observations be duly made : but Davis's 

 quadrant, the instrument generally used by British navigators, he perceived was 

 attended with this inconveniency, that the observer must bring the shade or 

 spot of light from the sun, and the rays from the horizon, to coincide exactly 

 on the fiducial edge of the horizontal vane : that though this can be done in 

 moderate weather and seas, with a clear sky, and when the sun is not too high, 

 without any great difficulty ; yet in other cases it requires more accuracy than 

 can in some junctures possibly be applied, and more time than can be allowed 

 for it. In European latitudes, or to those nearer the northern tropic, when the 

 sun is in the southern signs, and near tlie meridian, he rises and falls but slow- 

 ly : yet in voyages to the East and West Indies, of which many are made, he 

 is at noon often, and for many days together, in or near the zenith, and when 

 approaching to, or leaving it, he rises and falls, when he has declination, faster 

 than even at the horizon ; for it is well known to persons acquainted with the 

 sphere, that when his diurnal course takes the zenith, he there rises and falls a 



