C986) 
H I. LeSiures ini CoHeClions tmAe hy Robert Hooke, Secfe» 
tAYj of the R. Society. Frmted for J. Mart} n, Printer ta 
rA(rR.Society,i678. 
THe Work is divided by the Learned Author into two 
Parc^ The fir ft is called containing, befides 
Obfervationsof theCometsof i6j54,j665',and 1677, dif- 
courfe alfo on Comets in general. As amongft other particu- 
lars, of the Wtzdy Nucl€U4,i and BUze, That this isfiot al- 
ways oppofite to the Sun, Their Magnitude, Subflance; 
thoughr, bythe Author, loofe and confufible; as fronvthe 
variation of the Magnetica! direflion,he fuppofeth that alfo 
of the inner parts of ihe Earth to be. Denfity, Mutability, 
DilToluiion^Fluidity, Gravity, Light, Fjgure,Motion3 whe- 
ther bended or ftrair, with equal or uaequai velocity, &c. 
A Digreflionof ihe method of Speculating the great and firfl 
Principles of ihellniverfe^Theory of Comcts,asto Parallax 
hitherto defe^ive. What the World expefls from Ur.Heve- 
liH4, Parallaxes arifing from Hypothefes of the proper 
motions either of the Earth, or Comet, or both together 
ccnfider^d, arife to a certainty of the Magnitude of Comets-: 
others ,depending on other fuppofitions, not. Allowing ine- 
quality, of Motion, and more compounded Curve Lines, 
nothing can be determined* A gravitation towards the Sun, 
makes out the Mo:ron of the Gomer, and direftion of the 
Blaze. Comers wafte in the<u^/A^r, which isas a Menftri>.. 
urn CO difTolve them. The way of enquiring Parallax by Te» - 
lefcopes further explained* A fecond way by too Obfervers 
a ta diftance propounded : A third way of Sr, Chrifl, Wren^ 
his Ma jefties Surveyor GeneraT, fet dow n and demonftrated 
by a Geometrical" Probleme, an Invention altogether new. 
And how exaflly all the Obfervations he bad of the above- 
faid Comets, werejnade out by it; together with his own 
Schemes. Communicated Febr, 1 66f. 
Speakingof the nature of the Blaze ^ iotroduceth a Dif- 
cpurfeof the Honourable MnBt?)'/^, y^. A Memorial of fome 
Obfervations made upon an Artificial fubflance, in the pof- 
feflton of Mr. Cr^/z a famous Ger/»4» Chymift, thatfhines 
wiihour.any precedent iiluftr^tion. Wterein, amongft other 
35articufars,isobferved, that two fpoonfuls of matter did 
enlKghtt^ a large Glafs-fphere. Liquor fiiaken, had a finoke 
