(H0> 
writing before the Rdyal Society, thQ2i March 1666. by Mri 
Hook: as follows ; 
Having a great defirc(faith he) Co obferve the Body of Marr^ 
whilft Acronycal and Retrograde (having formerly with aGlafs 
of about I s^foot long, obfervM fome kind of Spots in the Face 
of it, ) though it be not at prefent in the PeriheUum of its Orbe, 
but nearer its Jphelitm 5 yet I found, that the Face of it, when 
neer its Oppoficion to the Sun ( with a Charge, the g(J.foote 
glafs, I made ufe off, would well bear ) appeared very near as 
bigj asthat oftheMoontothew^/^^eye^ which I found, by 
comparing it with the Full Moon , near adjoyning to it, 
March 10. 
But fuch had been the illdifpofition ofthe Airforfeveral 
nightSj that from more than 20. Obfervations of it, which I had 
made fince its being J{etrogr^de, I could find nothing of latis- 
facSlion, though 1 often imagined, Ifaw Spots, yet the Z^^^^^/t/^ 
veins of the Air ( if I may fo call thole parts, which, being inter- 
fpers'd up and down in it^ have a greater or lefs Refra(9:ive 
power, than the Air next adjoyning, with which they are 
mixt) did make it fo confus'd and glaring, that I could noc 
conclude upon any thing. 
On the third of March^ though the Air were ftill bad enough 
yet I could fee now and then the Body of il/^r/ appearing of 
the form A; which I prefently defcribed by z Scheme; and 
about 1 04 minutes after, as cxad:ly reprefenting what I faw 
through the Glafs, as I could, \ Ax t^i\\Q Scheme'^. This I was 
fufHciently fatisfied ( by very often obferving it through the 
Tube, and changing my Ey^ into various pofitions, thatfo 
there might be no kind of Fallacy in it ^ could be nothing elfe, 
but fome more Dusk^yzviA Spotted parts ofthe Face of this 
Planet. ' 
March 10. finding the Air very bad, I made ufe of a very 
fliallow Eye-glafs, as finding nothing with the greater 
Charge I and faw the appearance of it as in C, which I imagin'd, 
mightbe the Reprefentation of the former Spots by a leffer 
charge. About 5 ofthe Clock the fame morning, the Air be- 
ing very bad ( though to appearance exceeding clear, andcau- 
fing all the Stars to twinckle^and the minute Stars to appear ve- 
ry thick ) the Body feemM like D > which I ftill fuppos'd to be 
