FIG. PAGE
1.The heavens according to Ptolemy[3]
2.The zodiac of Denderah[7]
3.Illustration of Euclid’s statements[10]
4.The plane of the ecliptic[13]
5.The plane of the ecliptic, showing the inclination of the earth’s axis[14]
6.The first meridian circle[20]
7.The first instrument graduated into 360° (west side)[21]
8.Astrolabe (armillæ æquatoriæ of Tycho Brahe) similar to the one contrived by Hipparchus[26]
9.Ecliptic astrolabe (the armillæ zodiacales of Tycho Brahe), similar to the one used by Hipparchus[28]
10.Diagram illustrating the precession of the equinoxes[31]
11.Revolution of the pole of the equator round the pole of the ecliptic caused by the precession of the equinoxes[32]
12.The vernal equinox among the constellations, B.C. 2170[34]
13.Showing how the vernal equinox has now passed from Taurus and Aries[34]
14.Instrument for measuring altitudes[35]
15.Portrait of Tycho Brahe (from original painting in the possession of Dr. Crompton, of Manchester)[39]
16.Tycho Brahe’s observatory on the island of Huen[43]
17.Tycho Brahe’s system[46]
18.The quadrans maximus reproduced from Tycho’s plate[48]
19.Tycho’s sextant[50]
20.View and section of a prism[56]
21.Deviation of light in passing at various incidences through prisms of various angles[57]
22.Convergence of light by two prisms base to base[59]
23.Formation of a lens from sections of prisms[60]
24.Front view and section of a double convex lens[61]
25.Double concave, plane concave, and concavo-convex lenses[61]
26.Double convex, plane convex, and concavo-convex lenses[62]
27.Convergence of rays by convex lens to principal focus[62]
28.Conjugate foci of convex lens[63]
29.Conjugate images[64]
30.Diagram explaining Fig. [29][64]
31.Dispersion of rays by a double concave lens[65]
32.Horizontal section of the eyeball[66]
33.Action of eye in formation of images[68]
34.Action of a long-sighted eye[69]
35.Diagram showing path of rays when viewing an object at an easy distance[70]
36.Action of short-sighted eye[71]
37.Galilean telescope[73]
38.Telescope[75]
39.Diagram explaining the magnifying power of object-glass[76]
40.Scheiner’s telescope[78]
41.Dispersion of light by prism[80]
42.Diagram showing the amount of colour produced by a lens[81]
43.Decomposition and recomposition of light by two prisms[83]
44.Diagram explaining the formation of an achromatic lens[84]
45.Combination of flint- and crown-glass lenses in an achromatic lens[86]
46.Diagram illustrating the irrationality of the spectrum[87]
47.Diagram illustrating the action of a reflecting surface[91]
48.Experimental proof that the angle of incidence = angle of reflection[92]
49.Convergence of light by concave mirror[94]
50.Conjugate foci of convex mirror[94]
51.Formation of image of candle by reflection[95]
52.Diagram explaining Fig. [51][96]
53.Reflection of rays by convex mirror[98]
54.Reflecting telescope (Gregorian)[101]
55.Newton’s telescope[102]
56.Reflecting telescope (Cassegrain)[103]
57.Front view telescope (Herschel)[103]
58.Diagram illustrating spherical aberration[105]
59.Diagram showing the proper form of reflector to be an ellipse[106]
60.Huyghens’ eyepiece[110]
61.Diagram explaining the achromaticity of the Huyghenian eyepiece[111]
62.Ramsden’s eyepiece[112]
63.Erecting or day eyepiece[113]
64.Images of planet produced by short and long focus lenses, &c.[123]
65.Showing in an exaggerated form how the edge of the speculum is worn down by polishing[128]
65*.Section of Lord Rosse’s polishing machine[131]
66.Mr. Lassell’s polishing machine[132]
67.Simple telescope tube, showing arrangement of object-glass and eyepiece[140]
68.Appearance of diffraction rings round a star when the object-glass is properly adjusted[141]
69.Appearance of same object when object-glass is out of adjustment[141]
70.Optical part of a Newtonian reflector of ten inches aperture[143]
71.Optical part of a Melbourne reflector[143]
72.Mr. Browning’s method of supporting small specula[144]
73.Support of the mirror when vertical[146]
74.Division of the speculum into equal areas[147]
75.Primary, secondary, and tertiary systems of levers shown separately[148]
76.Complete system consolidated into three screws[148]
77.Support of diagonal plane mirror (Front view)[150]
78.Support of diagonal plane mirror (Side view)[150]
79.A portion of the constellation Gemini seen with the naked eye[154]
80.The same region, as seen through a large telescope[155]
81.Orion and the neighbouring constellations[156]
82.Nebula of Orion[157]
83.Saturn and his moons[160]
84.Details of the ring of Saturn[161]
85.Ancient clock escapement[177]
86.The crown wheel[178]
87.The clock train[180]
88.Winding arrangements[181]
89.The cycloidal pendulum[185]
90.Graham’s, Harrison’s, and Greenwich pendulums[188]
91.Greenwich clock: arrangement for compensation for barometric pressure[194]
92.The anchor escapement[197]
93.Graham’s dead beat[199]
94.Gravity escapement (Mudge)[200]
95.Gravity escapement (Bloxam)[202]
96.Greenwich clock escapement[204]
97.Compensating balance[207]
98.Detached lever escapement[208]
99.Chronometer escapement[209]
100.The fusee[209]
101.Diggs’ diagonal scale[213]
102.The vernier[214]
103.System of wires in a transit eyepiece[220]
104.Wire micrometer[221]
105.Images of Jupiter[224]
106.Object-glass cut into two parts[225]
107.The parts separated, and giving two images of any object[225]
108.Double images seen through Iceland spar[227]
109.Diagram showing the ordinary and extraordinary rays in a crystal of Iceland spar[227]
110.Crystals of Iceland spar[228]
111.Double image micrometer[229]
112.Tycho Brahe’s mural quadrant[235]
113.Transit instrument (Transit of Venus Expedition)[236]
114.Transit instrument in a fixed observatory[237]
115.Diagram explaining third adjustment[239]
116.The mural circle[241]
117.Transit circle, showing the addition of circles to the transit instrument[242]
118.Perspective view of Greenwich transit circle[243]
119.Plan of the Greenwich transit circle[245]
120.Cambridge (U.S.) meridian circle[248]
121.Diagram illustrating how the pole is found[249]
122.Diagram illustrating the different lengths of solar and sidereal day[255]
123.System of wires in transit eyepiece[257]
124.The Greenwich chronograph. (General view)[261]
125.Details of the travelling carriage which carries the magnets and prickers. (Side view and view from above)[262]
126.Showing how on the passage of a current round the soft iron the pricker is made to make a mark on the spiral line on the cylinder[263]
127.Side view of the carriage carrying the magnets and the pointer that draws the spiral[263]
128.Wheel of the sidereal clock, and arrangement for making contact at each second[266]
129.Arrangement for correcting mean solar time clock at Greenwich[268]
130.The chronopher[276]
131.Reflex zenith tube[286]
132.Theodolite[288]
133.Portable alt-azimuth[289]
134.The 40-feet at Slough[294]
135.Lord Rosse’s 6-feet[295]
136.Refractor mounted on alt-azimuth tripod for ordinary star-gazing[296]
137.Simple equatorial mounting[298]
138.Cooke’s form for refractors[300]
139.Mr. Grubb’s form applied to a Cassegrain reflector[301]
140.Grubb’s form for Newtonians[303]
141.Browning’s mounting for Newtonians[304]
142.The Washington great equatorial[309]
143.General view of the Melbourne reflector[312]
144.The mounting of the Melbourne telescope[313]
145.Great silver-on-glass reflector at the Paris observatory[316]
146.Clock governor[319]
147.Bond’s spring governor[320]
148.Foucault’s governor[323]
149.Illuminating lamp for equatorial[325]
150.Cooke’s illuminating lamp[326]
151.Dome[338]
152.Drum[338]
153.New Cincinnati observatory—(Font elevation)[338]
154.Cambridge (U.S.) equatorial[339]
155.Section of main building—United States naval observatory[341]
156.Foucault’s siderostat[344]
157.The siderostat at Lord Lindsay’s observatory[348]
158.Position circle[353]
159.How the length of a shadow thrown by a lunar hill is measured[354]
160.The determination of the angle of position of the axis of Saturn’s ring[358]
161.Measurement of the angle of position of the axis of a figure of a comet[359]
162.Double star measurement[360]
163.Ring micrometer[368]
164.Thermopile and galvanometer[374]
165.Rumford’s photometer[378]
166.Bouguer’s photometer[379]
167.Kepler’s diagram[387]
168.Newton’s experiment, showing the different refrangibilities of colours[388]
169.First observation of the lines in the solar spectrum[391]
170.Solar spectrum[392]
171.Student’s spectroscope[393]
172.Section of spectroscope[394]
173.Spectroscope with four prisms[396]
174.Automatic spectroscope (Grubb’s form)[397]
175.Automatic spectroscope (Browning’s form)[397]
176.Last prism of train for returning the rays[398]
177.Spectroscope with returning beam[399]
178.Direct-vision prism[399]
179.Electric lamp[404]
180.Electric lamp arranged for throwing a spectrum on a screen[405]
181.Comparison of the line spectra of iron, calcium, and aluminium, with common impurities[406]
182.Coloured flame of salts in the flame of a Bunsen’s burner[408]
183.Spectroscope arranged for showing absorption[409]
184.Geissler’s tube[413]
185.Spectrum of sun-spot[415]
186.Diagram explaining long and short lines[416]
187.Comparison of the absorption spectrum of the sun with the radiation spectra of iron and calcium, with common impurities[418]
188.Comparison prism[423]
189.Comparison prism[423]
190.Foucault’s heliostat[424]
191.Object-glass prism[426]
192.The eyepiece end of the Newall refractor[427]
193.Solar telespectroscope (Browning’s form)[428]
194.Solar telespectroscope (Grubb’s form)[428]
195.Side view of spectroscope[429]
196.Plan of spectroscope[429]
197.Cambridge star spectroscope elevation[430]
198.Cambridge spectroscope plan[430]
199.Direct-vision star spectroscope (Secchi)[431]
200.Types of stellar spectra[433]
201.Part of solar spectrum near F[436]
202.Distortions of F line on sun[438]
203.Displacement of F line on edge of sun[439]
204.Diagram showing the path of the ordinary and extraordinary ray in crystals of Iceland spar[445]
205.Appearance of the spots of light on the screen shown in the preceding figure, allowing the ordinary ray to pass and rotating the second crystal[446]
206.Appearance of spots of light on screen on rotating the second crystal, when the extraordinary ray is allowed to pass through the first screen[447]
207.Instrument for showing polarization by reflection[448]
208.Section of plate-holder[456]
209.Enlarging camera[458]
210.Instantaneous shutter[460]
211.Photoheliograph as erected in a temporary observatory for photographing the transit of Venus in 1874[461]
212.Copy of photograph taken during the eclipse of 1869[474]
213.Part of Beer and Mädler’s map of the moon[476]
214.The same region copied from a photograph by De La Rue[477]
215.Comparison between Kirchhoff’s map and Rutherfurd’s photograph[480]
216.Arrangement for photographically determining the coincidence of solar and metallic lines[481]
217.Telespectroscope with camera for obtaining photographs of the solar prominences[482]

BOOK I.
THE PRE-TELESCOPIC AGE.

STARGAZING: PAST AND PRESENT

CHAPTER I.
THE DAWN OF STARGAZING.

Some sciences are of yesterday; others stretch far back into the youth of time. Among these there is one of the beginnings of which we have lost all trace, so coeval was it with the commencement of man’s history; and that science is the one of which we have to trace the instrumental developments.

Although our chief task is to enlarge upon the modern, it will not be well, indeed it is impossible, to neglect the old, because, if for no other reason, the welding of old and new has been so perfect, the conquest of the unknown so gradual.

The best course therefore will be to distribute the different fields of thought and work into something like marked divisions, and to commence by dividing the whole time during which man has been observing the heavens into two periods, which we will call the Pre-telescopic and the Telescopic Ages. The work of the Pre-telescopic age of course includes all the early observations made by the unaided eye, while that of the Telescopic age includes those of vastly different kinds, which that instrument had rendered possible; so that it divides itself naturally into some three or four sub-ages of extreme importance.

It is unnecessary to say one word here on the importance of the invention of the telescope; it is well for the present purpose, however, to emphasize the further distinctions we obtain when we consider the various additions made from time to time to the telescope.

The Telescope, in fact, was comparatively little used until astronomy annexed that important branch of physics to its aid which gave us a Clock—a means of dividing time in the most accurate manner.

In quite recent times the addition of the Camera to the Telescope marks an important advance; indeed the importance of photography is not yet recognised in the way it should be.