PROCEEDINGS OF THE SOCIETY. 1117 



Mr, Kaiu's note (in reply to a letter from Mr. Crisp) was as 

 follows : — 



" As you remark in your letter, there is considerable confusion in 

 regard to the matter of Tolu. I am unable to account for the differ- 

 ences, unless upon the suj)position that different samples of the gum 

 behave differently. By reference to the ' U. S. Dispensatory ' (15th 

 edition, 1883, Wood and Bache), I notice that there is a factitious 

 Balsam of Tolu containing about 60 per cent, of styrax. Now styrax 

 is soluble in benzole, and it is just possible that some experimenters 

 may have got hold of this factitious balsam. The following extract 

 from the same work may be of interest to you : — 



" ' It (Tolu) is entirely soluble in alcohol, and the solution shows 

 an acid reaction with test paper. It is almost insoluble in water and 

 benzine. Warm disuljihide of carbon removes from the balsam 

 scarcely anything but cinnamic and benzoic acids. On evaporating 

 the disulphide, no substance having the properties of resin should be 

 left behind. Boiling water extracts its acid,' 



" From the above, it would appear that the easiest way to get rid 

 of the acids, whose crystals are so objectionable, is to use disulphide 

 of carbon, water being objectionable on account of the difficulty in 

 getting rid of it by evaporation. I ought, perhaps, to add that my 

 use of benzole for that purpose was the result of an accident, I having 

 attempted to make a solution of the gum in benzole. After digesting 

 several days, none of the gum was dissolved, but the benzole yielded 

 beautiful crystals of cinnamic and benzoic acids upon evaporation." 



Mr. Kitten's note on a new diatom, Navicula Durrandii, was read 

 {ante, p, 1012). 



Mr. J. C. Stodder's note was read as follows : — 



" Inasmuch as I have noticed in your Journal occasional expres- 

 sions of the opinions of different microscopists as regards the formation 

 of a small battery of objectives which should cover reasonably well 

 all the requirements of the general Microscopist, and inasmuch as I 

 have never seen any published statement of the views held upon this 

 subject by the late Mr. E. B. ToUes, I venture to send you a copy of 

 a memorandum which I have just foimd among my loose microscopical 

 papers. 



' Boston, May 26th, 1882. 



Meeting Mr. E. B. ToUes to-day at the office of Mr. Charles 

 Stodder, I asked him what he thought was the best scries of, say, 

 four or five objectives to cover as well as possible the whole range of 

 ' general microscopy.' He answered, after some reflection : — 



' For four only— 3 in., 1 in, 30'', 4/10 in. IIO"" dry, 1/10 in.— 

 oil-glycerin-water immersion, which will work through 1/100 in. 

 covers, and shfjuld have a balsam angle of not much less than 120° 

 for best results,' He added : ' An excellent and useful lens to add to 

 the above series would bo a 1/5 in. 110'^ or 120^ dry' " (ante, p, 863). 



Mr, C. D. Ahrens' paper on "An improved Form of Stephenson's 

 Erecting and Binocular Prisms " was read, in wliich he proposed to 



