132.

Of the difference between light and lustre; and that lustre is not
included among colours, but is saturation of whiteness, and derived
from the surface of wet bodies; light partakes of the colour of the
object which reflects it (to the eye) as gold or silver or the like.

133.

OF THE HIGHEST LIGHTS WHICH TURN AND MOVE AS THE EYE MOVES WHICH
SEES THE OBJECT.

Suppose the body to be the round object figured here and let the
light be at the point _a_, and let the illuminated side of the
object be _b c_ and the eye at the point _d_: I say that, as lustre
is every where and complete in each part, if you stand at the point
_d_ the lustre will appear at _c_, and in proportion as the eye
moves from _d_ to _a_, the lustre will move from _c_ to _n_.

134.

OF PAINTING.

Heigh light or lustre on any object is not situated [necessarily] in
the middle of an illuminated object, but moves as and where the eye
moves in looking at it.

135.

OF LIGHT AND LUSTRE.

What is the difference between light and the lustre which is seen on
the polished surface of opaque bodies?

The lights which are produced from the polished surface of opaque
bodies will be stationary on stationary objects even if the eye on
which they strike moves. But reflected lights will, on those same
objects, appear in as many different places on the surface as
different positions are taken by the eye.

WHAT BODIES HAVE LIGHT UPON THEM WITHOUT LUSTRE?

Opaque bodies which have a hard and rough surface never display any
lustre in any portion of the side on which the light falls.

WHAT BODIES WILL DISPLAY LUSTRE BUT NOT LOOK ILLUMINATED?

Those bodies which are opaque and hard with a hard surface reflect
light [lustre] from every spot on the illuminated side which is in a
position to receive light at the same angle of incidence as they
occupy with regard to the eye; but, as the surface mirrors all the
surrounding objects, the illuminated [body] is not recognisable in
these portions of the illuminated body.

136.

The relations of luminous to illuminated bodies.

The middle of the light and shade on an object in light and shade is
opposite to the middle of the primary light. All light and shadow
expresses itself in pyramidal lines. The middle of the shadow on any
object must necessarily be opposite the middle of its light, with a
direct line passing through the centre of the body. The middle of
the light will be at _a_, that of the shadow at _b_. [Again, in
bodies shown in light and shade the middle of each must coincide
with the centre of the body, and a straight line will pass through
both and through that centre.]

[Footnote: In the original MS., at the spot marked _a_ of the first
diagram Leonardo wrote _primitiuo_, and at the spot marked
_c_--_primitiva_ (primary); at the spot marked _b_ he wrote
_dirivatiuo_ and at _d deriuatiua_ (derived).]

Experiments on the relation of light and shadow within a room
(137--140).

137.

SHOWS HOW LIGHT FROM ANY SIDE CONVERGES TO ONE POINT.

Although the balls _a b c_ are lighted from one window,
nevertheless, if you follow the lines of their shadows you will see
they intersect at a point forming the angle _n_.

[Footnote: The diagram belonging to this passage is slightly
sketched on Pl. XXXII; a square with three balls below it. The first
three lines of the text belonging to it are written above the sketch
and the six others below it.]

138.

Every shadow cast by a body has a central line directed to a single
point produced by the intersection of luminous lines in the middle
of the opening and thickness of the window. The proposition stated
above, is plainly seen by experiment. Thus if you draw a place with
a window looking northwards, and let this be _s f_, you will see a
line starting from the horizon to the east, which, touching the 2
angles of the window _o f_, reaches _d_; and from the horizon on the
west another line, touching the other 2 angles _r s_, and ending at
_c_; and their intersection falls exactly in the middle of the


<< previous page | next page >>

Jump to page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 | 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107 | 108 | 109 | 110 | 111 | 112 | 113 | 114 | 115 | 116 | 117 | 118 | 119 | 120 | 121 | 122 | 123 | 124 | 125 | 126 | 127 | 128 | 129 | 130 | 131 | 132 | 133 | 134 | 135 | 136 | 137 | 138 | 139 | 140 | 141 | 142 | 143 | 144 | 145 | 146 | 147 | 148 | 149 | 150 | 151 | 152 | 153 | 154 | 155 | 156 | 157 | 158 | 159 | 160 | 161 | 162 | 163 | 164 | 165 | 166 | 167 | 168 | 169 | 170 | 171 | 172 | 173 | 174 | 175 | 176 | 177 | 178 | 179 | 180 | 181 | 182 | 183 | 184 | 185 | 186 | 187 | 188 | 189 | 190 | 191 | 192 | 193 | 194 | 195 | 196 | 197 | 198 | 199 | 200 | 201 | 202 | 203 | 204 | 205 | 206 | 207 | 208 | 209 | 210 | 211 | 212 | 213 | 214 | 215 | 216 | 217 | 218 | 219 | 220 | 221 | 222 | 223 | 224 | 225 | 226 | 227 | 228 | 229 | 230 | 231 | 232 | 233 | 234 | 235 | 236 | 237 | 238 | 239 | 240 | 241 | 242 | 243 | 244 | 245 | 246 | 247 | 248 | 249 | 250 | 251 | 252 | 253 | 254 | 255 | 256 | 257 | 258 | 259 | 260 | 261 | 262 | 263 | 264 | 265 | 266 | 267 | 268 | 269 | 270 | 271 | 272 | 273 | 274 | 275 | 276 | 277 | 278 | 279 | 280 | 281 | 282 | 283 | 284 | 285 | 286 | 287 | 288 | 289 | 290 | 291 | 292 | 293 | 294 | 295 | 296 | 297 | 298 | 299 | 300 | 301 | 302 | 303 | 304 | 305 | 306 | 307 | 308 | 309 | 310 | 311 | 312 | 313 | 314 | 315 | 316 | 317 | 318 | 319 | 320 | 321 |