70 Notices respecting New Books. 



hended by that class of people. It is not my object, however, to 

 deal with what may be called the picturesque in astronomy. I have 

 proposed it to myself as a special object, to show what may be com- 

 prehended, by persons possessing common understandings and ordi- 

 nary education, in the more elevated operations of astronomical 

 Bcience. The lectures will be, therefore, of what I may call a mathe- 

 matical kind. But in speaking of this, I beg that the ladies present 

 will not be startled. 1 do not mean to use algebra or any other 

 science, such as must be commonly of an unintelligible character to 

 a mixed meeting. When I use the word mathematical, I mean that 

 it will be my object to show how the measure of great things may 

 be referred to the measure of smaller things ; or to sum up in few 

 words, it will be my object, in an intelligible way, to show the great 

 leading stei)s of the process, by which the distance of the sun and 

 the stars is ascertained by a yard measure — the process by which the 

 weight of the sun and the planets is measured by the pound weight 

 avoirdupois. Occasionally I shall be prepared to go into details ; 

 but my principal business will be to show the great steps upon which 

 those who wish to study astronomy may enter, and by which they 

 may attain a general comprehension of the rules which will lead 

 them from one step to another." — Pp. 3, 4. 



This design has been kept steadily in view throughout the course, 

 but it is not possible to convey any idea of the author's method or 

 success by extracts. We would however call attention to the ma- 

 sterly analysis of one problem of considerable intricacy, viz. the de- 

 termination of the parallax of the sun, and consequently of his di- 

 stance, by observations of the transit of Venus. As this is the con- 

 necting link between measures upon the earth's surface and the 

 dimensions of our system, great pains have been taken to make the 

 process intelhgible. The further step of investigating the parallax, 

 and consequently the distance of the fixed stars (where that is prac- 

 ticable), is also elucidated ; and the author, with evident satisfaction, 

 thus sums up the several steps. " By means of a yard measure, a 

 base-line in a survey was measured ; from this, by the triangulations 

 and computations of a survey, an arc of meridian on the earth was 

 measured ; from this, with proper obseiTations with the zenith sector, 

 the surveys being also repeated on different parts of the earth, the 

 earth's form and dimensions were ascertained ; from these, and a 

 previous independent knowledge of the proportions of the distances 

 of the earth and other planets from the sun, with observations of the 

 transit of Venus, the sun's distance is determined; and from this, 

 with observations leading to the parallax of the stars, the distance 

 of the stars is determined. And every step in the process can be 

 distinctly referred to its basis, that is, the yard measure." — P. 191. 



In a similar manner, through the Schehallien and Cavendish 

 experiments, the density of the earth is ascertained, i. e. that it is 

 between five and six times as heavy as a corresponding bulk of water ; 

 and as its dimensions are known, the weight of the earth in pounds 

 avoirdupois can be readily assigned. Having the dimensions of the 

 moon's orbit, the space through which the earth draws the moon in 



