VOL. XU.] PHILOSOPHICAL TRANSACTIONS. 383 



running transversely ; cc the third taking a different course ; dd the lower 

 edge, which is infixed to the head. 



Fig. 9, the shell or hemicranium, seen on the inside, with the process run- 

 ning across it, one end of which a is fixed, the other a is moveable. 



Fig. 10, A, B, c, D, the same as in fig. 8 ; e the hinge, by which these are 

 connected, and may easily dilate or open. 



Fig. 1 1 , AA the membrane covering the head, freed from the hemicrania, 

 which were attached to this membrane ; b the place, where the hemicrania 

 were connected ; c the middle anterior part, in which the tubercle was pro- 

 minent. 



Fig. 12, AA the membrane of fig. I I, separated and turned back; b the 

 pellucid pyriform body, lying in the middle of the head, and which formed ; 

 c the tubercle. 



Fig. 13, the two defences of the tail, of which the exterior part a, is gib- 

 bous, the other or interior b, is, as it were, hollowed : these extremities are 

 bifid, c, the part by which they are joined to the tail. 



Tmo Otservalions of Explosions in the j4ir ; one heard at HaUted in Essex, by 

 the Rev. A. Vievar ; the other by Sam. Shepheard, Esq. of Spring^ld. 

 N°455, p. 288. 



On Sunday the 12th of March 1731-2, between 1 and 2 o'clock in the 

 afternoon, walking in the garden, Mr. V. heard as it had been a loud clap of 

 thunder from the north-east. While looking into the air, the noise was re- 

 peated very loud, but seemed more like the violent fall of a house, so that he 

 expected every moment an out-cry from the town : but he was soon undeceived, 

 when it began again, and he found it made towards him, with a different noise 

 from the former, being like the grinding of flint stones, but very loud. Its 

 dimensions seemed to be about 3 feet wide. He found it sink in the air, and 

 as it seemed to point directly at his head, he laid himself down on a glass-slope, 

 to let it pass over. However, at the upper end of the walk it fell to the ground, 

 and came rolling down the grass-walk ; and he can compare it to nothing better 

 than to that of a violent grinding of flint-stones, or a coach and six at full 

 speed on a causeway of loose stones. He lay attentive, expecting to see some- 

 thing, and saw a piece of wood came running before it. When the pheno- 

 menon came to the water- side, it twisted up a large stake that stood in its way, 

 and tossed it towards him with much violence, and immediately fell into the 

 water, with the violence and noise of a red-hot mill-stone. He has seen tjje 



