26 



the day seventeen, in the night, twenty syllables. There 

 is an echo on the bank of the river Nassa, between Bin- 

 gen and Collentz in Germany, which repeats what is said 

 seventeen times. And what is still more peculiar, the 

 person who speaks is scarce heard at all, but the repeti- 

 tion clearly, and with surprising variety : the echo seem- 

 ing sometimes to approach nearer, and sometimes to be 

 farther off. One person hears only one voice, another se- 

 veral: one hears it on the right, another on the left. 



Two miles from Milan there is a still more surprising 

 echo. It returns the sound of a pistol fifty-six times. 

 The first repetitions follow one another very quick ; but 

 they are more distinct in proportion as they decay. 

 There are two parallel walls, which beat the sound back 

 upon each other. 



5. The fine effluvia from odorous bodies, when they 

 reach our nostrils, excite the sensation of smellijig. 

 Some bodies emit these most when they are moist: some 

 only when they are warmed or heated. From all such 

 bodies^ innumerable particles flow, which according to 

 their various size, figure, and motion, variously affect the 

 olfactory- nerve. But what particular motion, size, or 

 figure, is required in order to any particular smell, who 

 is able to explain? 



These effluvia indeed are inconceivably small : so that 

 amber and divers other odorous bodies, emit them for 

 many years, without any discernable loss, either as to 

 bulk or weight. 



Mr. Boyle shews, 1. That the nnmber of particles 

 thus emitted, is exceeding great. 2. That they are of a 

 very penetrating nature. 3. That they move with vast 

 swiftness and in all directions. 4. That there is often 

 a wonderful congruity between the bulk and shape of 

 these effluvia and the pores of the bodies they penetrate, 

 and lastly, that they may excite great motions, and 

 thereby make great changes in organized bodies. 



That effluvia are emitted to a very great distance we 

 learn from hence, that wines grow turbid in the hogs- 

 head, precisely at the time that the grapes are ripe in 



