OCTOBEE 18, 1895.] 



SCIENCE. 



505 



theodolite, the student may determine lati- 

 tude from circum-meridian altitudes of the 

 sun (Gauss' mode of reduction) and azi- 

 muth from simultaneous readings of the 

 vertical and horizontal circles when the 

 line of sight is directed to the sun, com- 

 bined with readings of the horizontal circle 

 when the telescope is directed upon a ter- 

 restrial mark. This mode of determining- 

 azimuth, although very much neglected in 

 the text-books, admits of considerable pre- 

 cision and is excellently adajited to the 

 purposes of the engineer. 



Thus far the student's jjroblems have 

 involved only work by daylight, but he 

 should now take up night work and will 

 require some instruction about illuminating 

 the wires of his instrument and in reading 

 verniers, levels, etc., by lamplight. His 

 first problem should be the simultaneous 

 determination of time and latitude from 

 equal altitudes of Polaris and southern 

 stars. This method is very little used 

 in America, but it is the best method of 

 using an engineer's transit for the deter- 

 mination of either time or latitude and 

 should be taught to engineers. An exposi- 

 tion of the method with examples of its 

 application has been given by the author of 

 this paper in the Bulletin of the University 

 of Wisconsin, Science Series, Vol. I., No. 3. 



An average student with a good transit 

 and ordinary watch may be exj)ected within 

 an hour to determine his latitude within 2" 

 and the error of his watch within a quarter 

 of a second. 



The limits of time above allotted permit 

 the assignment of only one more problem 

 in our course, the determination of azimuth 

 from observations of a close circum-polar 

 star. The student should be taught that 

 while it is advantageous to observe at 

 elongation it is by no means necessary to 

 do so, and that by a proper combination of 

 stars, together with an approximate deter- 

 mination of time, he may frequently avoid 



the necessitj^ of observing at inconvenient 

 hours without in any way impairing the 

 pi'ecision of his results. 



In outlining the above required course, 

 to be given in sixty exercises, or less, no 

 reference has been made to a text-book, and 

 the author knows of no text-book which is 

 altogether satisfactorJ^ In giving at the 

 University of Wisconsin the equivalent of 

 the course above outlined it has been his 

 practice to prepare cyclo-style copies of 

 lecture notes covering the ground to be 

 traversed by the class and including in de- 

 tail the record and reduction of a set of ob- 

 servations corresponding to each problem 

 assigned the student. A copj' of these 

 notes is placed in the hands of each student 

 and he is expected to familiarize himself 

 with the text contained in them and to use 

 the numerical parts as models for the record 

 and reduction of his own observations. 

 These observations and their reduction 

 written up in a note-book and accompanied 

 by the requisite formulse are preserved by 

 the student as guides for any future work 

 of the kind which he may have occasion to 

 do. This mode of instruction, however, 

 cannot be regarded as altogether satisfac- 

 tory, and a suitable text-book would pre- 

 sumably strengthen the course. 



It does not fall within the scope of this 

 paper to provide in detail an advanced elec- 

 tive course in astronomj\ As our schools 

 are organized such a course must be ar- 

 ranged to meet the requirements of each 

 individual case, but the material available 

 for such a course in a properlj^ equipped 

 engineering observatory may be indicated 

 as follows: 



The Transit Instrument. Determination 

 of time in the meridian. Investigation of 

 the constants of the instrument. Deter- 

 mination of azimuth by mounting the in- 

 strument in the vertical of a circum-polar 

 star near elongation. 



Clocks and Chronometers. Comparison 



