The Copy of a Letter to Signore GALILÆO
GALILÆI, Chief Philoſopher to the moſt Serene
Great Duke of TVSCANY.
GALILÆI, Chief Philoſopher to the moſt Serene
Great Duke of TVSCANY.
In ſatisfaction of my promiſe, in my former Letters of
repreſenting unto you ſome of my Conſiderations
made upon the Lake Thraſimeno, I ſay, That in times
paſt, being in Perugia, where we held our General
Convention, having underſtood that the Lake Thraſimeno, by
the great drought of many Moneths was much abated, It came
into my head, to go privately and ſee this novelty, both for my
particular ſatisfaction, as alſo that might I be able to relate the
whole to my Patrons, upon the certitude of my own ſight of the
place. And ſo being come to the Emiſſary of the Lake, I found
that the Level of the Lakes ſurface was ebbed about five Ro
man Palmes of its wonted watermark, inſomuch that it was lower
than the tranſome of the mouth of the Emiſſary, by the length
of ----------------------------this deſcribed line, and there
fore no Water iſſued out of the Lake, to the great prejudice of
all the places and villages circumjacent, in regard that the Wa
ter which uſed to run from the ſaid Lake turned 22 Mills, which
not going, neceſſitated the inhabitants of thoſe parts to go a
dayes journey and more, to grinde upon the Tiber. Being retur
ned to Perugia, there followed a Rain, not very great, but con
ſtant, and even, which laſted for the ſpace of eight hours, or
thereabouts; and it came into my thoughts to examine, being
in Perugia, how much the Lake was increaſed and railed by this
Rain, ſuppoſing (as it was probable enough) that the Rain had
been univerſal over all the Lake; and like to that which fell in
Perugia, and to this purpoſe I took a Glaſſe formed like a Cy
linder, about a palme high, and half a palme broad; and having
put in water ſnfficient to cover the bottome of the Glaſſe, I no
ted diligently the mark of the height of the Water in the Glaſſe,
and afterwards expoſed it to the open weather, to receive the
Raine-water, which fell into it; and I let it ſtand for the
ſpace of an hour; and having obſerved that in that time the Wa
ter was riſen in the Veſſel the height of the following line---,
I conſidered that if I had expoſed to the ſame rain ſuch other veſ
ſels equal to that, the Water would have riſen in them all accor
ding to that meaſure: And thereupon concluded, that alſo in all
repreſenting unto you ſome of my Conſiderations
made upon the Lake Thraſimeno, I ſay, That in times
paſt, being in Perugia, where we held our General
Convention, having underſtood that the Lake Thraſimeno, by
the great drought of many Moneths was much abated, It came
into my head, to go privately and ſee this novelty, both for my
particular ſatisfaction, as alſo that might I be able to relate the
whole to my Patrons, upon the certitude of my own ſight of the
place. And ſo being come to the Emiſſary of the Lake, I found
that the Level of the Lakes ſurface was ebbed about five Ro
man Palmes of its wonted watermark, inſomuch that it was lower
than the tranſome of the mouth of the Emiſſary, by the length
of ----------------------------this deſcribed line, and there
fore no Water iſſued out of the Lake, to the great prejudice of
all the places and villages circumjacent, in regard that the Wa
ter which uſed to run from the ſaid Lake turned 22 Mills, which
not going, neceſſitated the inhabitants of thoſe parts to go a
dayes journey and more, to grinde upon the Tiber. Being retur
ned to Perugia, there followed a Rain, not very great, but con
ſtant, and even, which laſted for the ſpace of eight hours, or
thereabouts; and it came into my thoughts to examine, being
in Perugia, how much the Lake was increaſed and railed by this
Rain, ſuppoſing (as it was probable enough) that the Rain had
been univerſal over all the Lake; and like to that which fell in
Perugia, and to this purpoſe I took a Glaſſe formed like a Cy
linder, about a palme high, and half a palme broad; and having
put in water ſnfficient to cover the bottome of the Glaſſe, I no
ted diligently the mark of the height of the Water in the Glaſſe,
and afterwards expoſed it to the open weather, to receive the
Raine-water, which fell into it; and I let it ſtand for the
ſpace of an hour; and having obſerved that in that time the Wa
ter was riſen in the Veſſel the height of the following line---,
I conſidered that if I had expoſed to the ſame rain ſuch other veſ
ſels equal to that, the Water would have riſen in them all accor
ding to that meaſure: And thereupon concluded, that alſo in all