82 METHODS OF INSTRUCTION IN THE PHYSICAL SCIENCES 



junction : those of Lectures, employing that term in the sense 

 in which it is applied to the discourses on scientific subjects, 

 which are delivered in the theatres of Public Institutions and 

 of Medical Schools ; and Lessons to classes of pupils. The 

 former have been addressed to the entire school, or to several 

 of the classes into which it is arranged, assembled together ; 

 the latter, of course, to a smaller number of boys. 



The Lectures have in general been spoken from notes pre- 

 pared for the express use of this department in the Schools, 

 containing matter which would not have been offered when 

 addressing a public audience, or pupils more advanced in 

 education, and omitting many subjects which would with 

 propriety have been introduced, on such occasions. On ac- 

 count of the routine in which the business of a school is ne- 

 cessarily conducted, and of the comparatively small portion of 

 time that can be allowed, during the session, for the con- 

 struction and arrangement of apparatus and illustrations, 

 philosophical propriety of arrangement has sometimes been 

 purposely sacrificed to convenience of explanation. On this 

 account* also, it has been the endeavour of the Teacher to em- 

 ploy such instruments and pieces of permanent apparatus as 

 will admit experiments to be repeatedly exhibited with them, 

 without sensible injury, and with little re-preparation. Of this 

 description are the various forms of the Thermometer and the 

 Hygrometer; the Pulse-glass; Dr. Wollaston's Cryopho- 

 rus, or Frost-bearer, an instrument for freezing at a distance 

 from the point where cold is applied, by means of the cold 

 ensuing from the rapid evaporation of the water to be frozen ; 

 the miniature Steam-engine of the same philosopher ; and also 

 his Elementary Galvanic Battery, by which a platinum wire 

 may be ignited and fused, merely by dipping a single plate 

 of zinc and a plate of copper into a dilute acid. 



When Chemistry has been the subject, rarely more than two 

 distinct experiments have been shown in each Lecture, that 

 number, when fully explained, having been found as great as 

 could with propriety be introduced. In the preparation and 

 arrangement of apparatus and materials for the Lectures, as 

 well as in the performance of experiments during their deli very, 

 the Teacher has always been assisted by one or two boys, who 

 may have evinced a particular taste for the exercises of this 

 department, or whose friends have requested that their atten- 

 tion might be specifically directed to it. It has generally hap- 

 pened, from the last hour of "school" having been appropriated 

 to the Lectures, that the preparations have been required to be 

 made "out of school-hours"; and this has been voluntarily 

 done, frequently in lieu of play, with much zeal and attention. 



