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100 Berger Short Focus Lenses. A sectional view of a Berger Short Focus Lens attached to an Erecting" Transit Telescope. No. 1 and 2 Lenses. No. 1 Lens. The above lenses may be attached separately or together, as shown; for a complete description see opposite page.
101 The Berger Short Focus Lens Attachment. A very valuable addition to the engineer's outfit is found in the short focus lens attachment which has been brought out. The contrivance is simple, but, like many simple devices, is very effective in overcoming a practical difficulty. Probably every engineer has been annoyed by being obliged to sight a point a little too near for the telescope to focus. Most transit telescopes will not focus on a point much nearer than 6 or 6 feet (levels not nearer than 7 or 8 feet) away from the instrument, while it is frequently necessary to sight a point on the ground nearly under the transit, at a distance which is usually less than that. In mine surveying as well as inside of factory buildings, one frequently needs to sight a point overhead or on the walls and very near the transit. Ordinarily the only way out of the difficulty is to focus as nearly as possible and do the rest by a guess. As a further instance, one often finds in leveling, that it will be necessary to take a reading on a point very near the instrument, and has to resort to various means (all of them inaccurate) of getting around the difficulty. The attachment mentioned consists of a small aluminum tube containing a simple lens, which is attached in front of the objective. The lens is so placed in the tube that it can be accurately centered by means of 4 adjusting screws. The effect of this lens is of course to bring rays to a focus nearer to the objective, and thus enable the observer to focus a nearer object than would otherwise be possible. When the telescope will focus no nearer than 6 feet, the attached lens, marked 1, is ground so that it will focus objects 6 feet away when the objective tube is drawn away in. This allows the entire motion of the focusing slide for distances between 6 and 4 feet. For distances nearer than 4 feet a second lens may take the place of the first and will focus up to about 2| feet. If the two are used at once the distance is reduced to about two feet. With this pair of lenses there is no distance between two feet and infinity at which objects cannot be focused. The accuracy of work done with this attachment is in no way affected by the centering of the attached lens itself, as this is capable of perfect adjustment. The only way in which error can occur is through the imperfection of the objective tube. If the cylindrical surface of the object-head of the telescope on which the attachment is placed is not concentric with the optical axis of the telescope this error will enter into the adjustment of the attached short focus lens. This error, however, is never large on an instrument sent out by our firm. But even admitting that there may be some error here, it must be rememembered that this lens is never used for objects more than about 6 feet away ; consequently the resulting error on the point is entirely negligible, and the convenience of the attachment: 'n many cases is so great that it entirely outweighs any such consideration, since the work done at this distance will be entirely consistent with the work done with the instrument on the longer distances. The attachment fills a want that has long been felt by engineers and is certainly a step in advance in the perfection of instruments of precision. To attach this device to their old instruments it will be necessary to send the instrument to them, as every lens attachment must be specially fitted and centered. How- ever, it can be supplied with any of their new instruments, either Transits or Levels, made since 1899. When attached to transits, No. 1 permits focusing objects to about 3 feet, No. 2 permits focusing objects to about 2^ feet : both permit focusing objects to about 2 feet from center of instrument. This is so important a feature that one trial will convince one that it is indispensable to the outfit of an engineer The device is patented. The Messrs. Berger are also prepared to attach it to their Wye and Dumpy level, lor focusing nearly aa close as stated above for transits. For pi-ices see catalogue, page 203.
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ENGIN. LIBRARY UC-NRLF STANDARD INS
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PREFACE. THE instruments enumerated
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DESCRIPTION OP THE Essential Featur
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Tangent Screws. These are made of A
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The Finish. It is a well-known fact
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11 whatever. As a rule more harm th
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13 has sufficiently developed to im
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15 ordinary instruments, but it mus
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17 frame, and apply another drop of
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19 The finer and finest classes of
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21 applied with an adjusting pin ab
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23 adjustment of the telescope in t
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25 Owing to the many improvements m
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27 Engineers 9 Instruments and Thei
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ITrfpodfead 2 // Bolt 3 // >/ Mf J
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In practice, however, many engineer
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34 The Pancratic, or Changeable Pow
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the 130 division, and moved on unti
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38 Graduation Reading to 2O". A 15
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Decimal Vernier Graduation. For rai
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HORIZONTAL CIRCLE HORIZONTAL CIRCLE
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44 line of collimation of the teles
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46 Obviously then, the number of wh
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48 Gradienter Screw Table I. Factor
Page 56 and 57: 50 The subjoined table affords a re
Page 58 and 59: 52 Plumbing and Centering Arrangeme
Page 60 and 61: 54 To make the adjustment for Paral
Page 62 and 63: 56 capstan-headed screw at left to
Page 64 and 65: 58 To adjust the line of collimatio
Page 68 and 69: 62 The Adjustment of the Wye Level.
Page 70 and 71: On slightly rising ground locate fo
Page 72 and 73: (5.) Astronomical Triangle. The hei
Page 74 and 75: 68 From the -(- sign of the " diffe
Page 76 and 77: 70 Degree of Precision Required. (1
Page 78 and 79: 72 tions for refraction, using the
Page 80 and 81: 74 Correction to the Mean Refractio
Page 82 and 83: 76 Table H. Coefficients showing th
Page 84 and 85: 78 To Find the Meridian from " Pola
Page 86 and 87: 80 REMARKS. If the instrument is no
Page 88 and 89: 82 These devices are being more and
Page 90 and 91: 84 c. Directions. For finding the S
Page 92 and 93: 6. Directions. For reducing the nor
Page 94 and 95: 88 On Stadia Measurement. Written e
Page 96 and 97: 90 included between this and the ot
Page 98 and 99: 92 Jug, R, of the rod AB is the dif
Page 100 and 101: 94 gent screw of the main telescope
Page 102 and 103: 96 zero when plates are leveled up
Page 104 and 105: i I * 2 I! all 35 e 5c u fcc - = H
Page 108 and 109: 102 NOTE. In selecting instruments
Page 110: RIBBING PARTS OF INSTRUMENTS. Patro
Page 115: The Berber Complete Engineers' and
Page 119: [Patented) The Berber Complete Mine
Page 122 and 123: 11(5 5 O o to tO u tO CM in in in o
Page 124 and 125: 118 n ai in Spirit Levels. For the
Page 126 and 127: l, 33 120
Page 128 and 129: 122
Page 130 and 131: 14 124 C. L,. BEKGEK & SONS. BOSTON
Page 132 and 133: 1 5" AND 1 7|" C. t. BKKGER & SONS.
Page 134 and 135: C. 1-28 BEKGEU & SONS. Monitor Type
Page 136 and 137: 130 The Berger 18 MONITOR TYPE WYE
Page 138 and 139: 1 18 132 C. I*. BERGER & SONS, BOST
Page 140 and 141: 18 134 II ENGINEERS' WYE LEVEL. lev
Page 142 and 143: 136 18" HYDROGRAPHER'S WYE LEVEL Ha
Page 144 and 145: 138 Reversion Level. Applicable to
Page 146 and 147: 140 The Telescope will be invariabl
Page 148 and 149: 142 THE GEODETIC LEVEL. In response
Page 150 and 151: 144 COAST SURVEY PRECISE LEVEL The
Page 152 and 153: 146 PLANE TABLE This instrument, as
Page 154 and 155: 61" 150 ENGINEERS' AND SURVEYORS' T
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No. 1 a. 6 1 4 in. at edge of gradu
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No. I a. T 4 in. at edge of graduat
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No. 1 c. 154 C. L. BERGER & SO>S in
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No. 1 c, Style p. in. at edge of jr
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. 1 f. is made by C. L. Berger & So
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160 C. L. BEKGEK & SONS. MONITOR TY
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162 64 SURVEYORS' TRANSIT No. 1 s.
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5^" 164 C. L. BERGER & SONS, BOSTON
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166 C. L. BERGER & SONS. BOSTON 5|"
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5|" 168 ENGINEERS' AND SURVEYORS' T
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The Surveyors' Solar Attachment. Pl
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172 The Berger Solar Attachment Att
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174 Davis' Patent Solar Attachment.
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176 THE 5|" MOUNTAIN TRANSIT. This
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178 The 41" Mountain and Mining: Tr
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4|" 180 C. L,. BERGER & SONS. BOSTO
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182 The 4" Mountain, Mining and Rec
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184 The 4" Complete Transit- Theodo
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186 4>4 " Complete Mine Transit No.
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^ 188 t4 Mining Transits. All of th
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The 190 See M Fig. 1. Berger Patent
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03 192 Complete Mining Transit No.
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|S go Complete Wet-Mine Transit No.
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196 Different Types of Vertical Arc
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:i98 Edge G-racl nation for Vertica
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The Open-Frame Protected Vertical C
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202 C. L. BEKGKK & SONS. Flexible J
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S fa 204 Style of trivets used with
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200 Patented. The Lateral Adjuster
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Mining Transit. Interchangeable wit
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210 Tunnel Transits. Xo. 1C a Tunne
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212 Triaiigulatioii Transit- Theodo
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No. lib. 214 Complete Double Opposi
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210 No. 11 m. 7-iiich Complete Tran
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218 No. llg, 7-inch Complete Triang
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220 No. 12. 8-iiich Transit for Tri
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SPECIFICATIONS : No. 15 Alt-Azimuth
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No. 15 b. Alt.-Azimuth. 224 Alt. -A
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Portable Transit Instrument for Lat
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228 Reflecting Circle. Artificial H
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230 Current Meters, The types of cu
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232 Current Meters No. V and VI, As
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234 Plain Polar Plaiiimeter. This P
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236 Leveling Rods No. 145 No. 147 N
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Paine's Steel Tape Measures. & inch
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240 Surveyors' Chain Tapes. Heavy J
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2-12 Standard Steel Tape Measures.
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No. 210. Plummet Lamp. tfo. 212. 24
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246 Portable Anemometers. These ins
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PRICES SUBJECT TO CHANGE WITHOUT NO
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J Tripod Head 2 // Bolt 3 * .* Nut
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Levels, Locke's Hand Reversion Revo
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C. Li. Berger & Sons' Bevel-Limb Tr
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0) O (^ c CL 0? Z O (0 O K lu ffi C
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O CO K III III These prices do not
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ord (In whether . 4 O ~ bJD p,"* 3,
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a -iQ. Q u u o 0) o 0) U O U CO o C
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These prices do not include bag (SI
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Q III o o z o u o o U Ott bl CD O U
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o O (0 ui y O J O Q. O U 5> OC os .
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800290 I A 33012 Engineeringlibrary
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