VOL. VI.] PHILOSOPHICAL TRANSACTIONS; (JOJT 



the crooked part by a pair of compasses, the water was found to fill the cylinder 

 so near the half, that the difference could not be perceived; and the same held 

 proportionably at other depths. 



The proportion of the weight of salt water to that of fresh, was found by 

 weighing some ounces of both in a bottle whereof the weight was exactly known, 

 and which was made with so small a neck, that the addition or diminution of 

 one single drop in it was discernible. 



And that these trials may not be thought to have been made out of mere cu- 

 riosity, they will be found useful for those who have occasion to dive for reco- 

 vering things lost in water; since, by those experiments, they may beforehand 

 know, when they sink in the diving bell, or other fit instruments, to what depth 

 they can endure the compression of the air for respiration, and how they may 

 furnish themselves with air in a fit vessel for supply. 



Extracts of two Letters from Mr. Martin Lister to the Editor, dated 

 June 14, 1671? cind July 5,' I67I, concerning the Kind of Insect 

 hatched from the English Kermes, formerly taken notice of and de^ 

 scribed by the same in N" 71, p- 598. N" 73, p. 2196. 



June 10, I found several of the patellae kermiformes hatched in a box, where 

 I had purposely put them. They prove a sort of bees, as I guessed by the figure 

 of the worm, but certainly the least that I ever yet saw of that tribe, as not 

 much exceeding in their whole bulk the half of a pismire. They are very com- 

 pact and thick, of a coal-black colour. They seem to want neither stings, nor 

 the three balls in a triangle in their forehead, which yet are things to be referred 

 to the testimony of a microscope. What is very remarkable to the naked eye, 

 is a white or straw-coloured large and round spot on the back; of their four 

 wings the upper pair are shaded or dark-spotted, the undermost pair are clear. 

 We may entitle them, according to our custom, Apiculae nigrae, macula super 

 humeros sub-flavescente insignitae, e patellis sive favis membranaceis, veri ker- 

 mes similibus, suaque itidem purpura tingentibus, cerasi aut rosae aliarumve ar- 

 borum virgis adtextis, exclusae. ' 



Further Observations of the New Star near the BeaJc of Cygnus, in a 

 Letter from M. Hefelius, at Dantzick. Translated from the Latin, 

 iVr° 73, p. 2197. 



On April 29, 1 67 1 , I again observed the new star below the head of Cygnus, 

 and found it in the same place, near the milky way, where I saw it the former 

 year, from June and July to the 14th of October. It then however appeared 



