. Scientific American Volume 78 Number 01 (January 1898) . veying. It is an easy matter to measure the dimensions of aplot of ground, the size and location of the buildingsor other objects that may be on it, but on the water a Just before entering a harbor, the captain usually different process must be pursued. Not only is it ne-cessary to map the shoreline, and all the visible to-pography near it, but thedepth of the water andcharacter of the bottommust be minutely such a map is pro-perly drawn it forms a veryinteresting picture ofthat locality. A mapof this, sort is usuallycalled
. Scientific American Volume 78 Number 01 (January 1898) . veying. It is an easy matter to measure the dimensions of aplot of ground, the size and location of the buildingsor other objects that may be on it, but on the water a Just before entering a harbor, the captain usually different process must be pursued. Not only is it ne-cessary to map the shoreline, and all the visible to-pography near it, but thedepth of the water andcharacter of the bottommust be minutely such a map is pro-perly drawn it forms a veryinteresting picture ofthat locality. A mapof this, sort is usuallycalled a chart. The careful studyof a fine chart pro-duces just such anim pression on the eyeand mind as if wecould look down onthe scene from a bal-loon. We see all thehouses, hills, rocksand trees of the shoreand every undula-tion of the mud andsand on the bottom,with the water re-moved. Many milesof coast and harbormay thus be shownon one sheet of mod-erate size, with every-thing in its properproportion, shapeand position. To the ship captainthe depth of the. as triangulation. One way of doing this is by observ-ers stationed on the shore at two or more prominentplaces, and always in full view of the boat. Eachobserver follows the course of the sounding boat withthe telescope of his transit. For the benefit of those of our readers who may notbe familiar with surveying instruments, we would saythat a transit is an instrument having a telescope soattached to a graduated circle that its exact amountof rotation around its pivot may be noted. Conse-quently, the angle formed by the position of the boat,the transit station and some fixed object on the shoremay be very accurately and quickly determined, evento the small fraction of a degree. In a circle there are 360 degrees, each of which is sup-posed to be divided into 60 minutes, and each minuteinto as many seconds. Since a degree on the circleof the transit occupies a space of a pins head, itis, of course, impossible to subdivide each d
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