ABBREVIATIONS USED IN THE TEXT. 



(H) means high power, i.e. a magnifying power of 300 diameters linear. Such a magnifying power is 

 obtained by using a No. 7 objective, and a No. 3 eyepiece of Hartnack with the tube drawn out ; or 

 an English -inch objective and a medium eyepiece. 



(L) means low power, i.e. a magnifying power of 65 diameters linear. Such a magnifying power is 

 obtained by using a No. 3 objective and a No. 3 eyepiece of Hartnack with the tube drawn out ; or an 

 English one-inch objective and a medium eyepiece. 



T. S. and L. S. mean transverse and longitudinal section respectively. 



