Sec. 98. Soldering other Metals. Sec. 99. Brazing. Sec. 100. Silver Soldering. Sec. 101. On the Construction of Electrical Apparatus--Insulators. Sec. 102. Sulphur. Sec. 103. Fused Quartz. Sec. 104. Glass. Sec. 105. Ebonite or Hard Rubber. Sec. 106. Mica. Sec. 107. Use of Mica in Condensers. Sec. 108. Micanite. Sec. 109. Celluloid. Sec. 110. Paper. Sec. 111. Paraffined Paper. Sec. 112. Paraffin. Sec. 113. Vaseline, Vaseline Oil, and Kerosene Oil. Sec. 114. Imperfect Conductors. Sec. 116. Conductors. Sec. 117. Platinoid. Sec. 119. Platinum Silver. Sec. 120. Platinum Iridium. Sec. 121. Manganin. Sec. 122. Other Alloys. Sec. 123. Nickelin. Sec. 124. Patent Nickel. Sec. 125. Constantin. 126. Nickel Manganese Copper. CHAPTER IV. ELECTROPLATING AND ALLIED ARTS. Sec. 127. Electroplating. Sec. 128. The Dipping Bath. Sec. 130. Scratch-brushing. Sec. 131. Burnishing. Sec. 132. Silver-plating. Sec. 133. Cold Silvering. Sec. 134. Gilding. Sec. 135. Preparing Surfaces for Gilding. Sec. 136. Gilding Solutions. Sec. 137. Plating with Copper. Sec. 138. Coppering Aluminium. Sec. 140. Alkaline Coppering Solution. Sec. 141. Nickel-plating. 142. Miscellaneous Notes on Electroplating. Sec. 143. Blacking Brass Surfaces. Sec. 144. Sieves. Sec. 145. Pottery making in the Laboratory. APPENDIX. PLATINISING GLASS. PREFACE EXPERIMENTAL work in physical science rests ultimately upon the mechanical arts. It is true that in a well-appointed laboratory, where apparatus is collected together in greater or less profusion, the appeal is often very indirect, and to a student carrying out a set experiment with apparatus provided to his hand, the temptation to ignore the mechanical basis of his work is often irresistible. It often happens that young physicists are to be found whose mathematical attainments are adequate, whose observational powers are perfectly trained, and whose general capacity is unquestioned, but who are quite unable to design or construct the simplest apparatus with due regard to the facility with which it ought to be constructed. That ultimate knowledge of materials and of processes which by long experience becomes intuitive in the mind of a great inventor of course cannot be acquired from books or from any set course of instruction. There are, however, many steps between absolute ignorance and consummate knowledge of the mechanical arts, and it is the object of the following pages to assist the young physicist in making his first steps towards acquiring a working knowledge of "laboratory arts." However humble the ambition may be, no one can be more keenly alive than the writer to the inadequacy of his attempt; and it is only from a profound sense of the necessity which exists for some beginning to be made, that he has had the courage to air his views on matters about which there are probably hundreds or thousands of people whose knowledge is superior to his own.