50 CULTIVATION OF DIATOMS. 



deranged, and they can be observed with any kind of objective, pro- 

 vided that it has a correction sufficient for this length. As 

 the instrument is admirably adapted for photography ('), photographs 

 of high magnification can also be effected at any given moment. I 

 have for several years used with this instrument a glass shade which 

 covers up every optical part excepting the ocular ; the culture cells can 

 then rest in position, and the instrument be always ready for examina- 

 tion without any need of moving the shade. 



ZA Mr, C. Haughton Gill's Cultivations. 



Dr. Miquel has found in Mr. C. Haughton Gill (whose other in- 

 genious researches I shall describe hereafter) a worthy rival 

 in producing his cultivations. In short, this skilful chemist, who died 

 of heart disease while still at his work and at an age when he might 

 fairly have looked forward to many more years of life, commenced his 

 cultivations in 1891, but he had not at that time discovered the best 

 way of proceeding ; moreover with the modesty which characterised the 

 man, he attributed to Dr. Miquel all the success of his cultivations. 

 "I have wasted," he wrote me, "half my time in preliminary researches 

 and experiments, so that Dr. Miquel is in every way entitled to claim 

 priority." I shall here summarily extract from his correspondence with 

 me the information I possess concerning Mr. Gill's cultivations. I 

 consider that I am only discharging a debt of honour by publishing this 

 information, which my friend was prevented from giving to the world 

 himself by his sudden death. 



The liquid which appeared to Mr. Gill to be the best for culti- 

 vation was composed as follows : 

 A. Sodium chloride ... 



Sodium sulphate ... 



Potassium nitrate 



Acid Potassium phosphate 



Water 



B. Filtered spring water 

 Solution A 



10 parts by weight. 



5 > " 



2-5 > >> 



2'5 5> >> 



100 



100 parts by volume. 



'5 



To this solution he added a sufficient quantity of slaked lime to 

 neutralise the acidity of the liquid and a small quantity of well-washed 

 precipitated silica. Then subsequently he also added a small quantity 

 of either a sterilised infusion of grass or " Diatom-soup," which he obtained 

 by boiling a large quantity of fresh diatoms for a long time in water. 



( ' ) See " The Microscope," by Dr. H. Van Heurck, English Edition, London, 1893, pp. 255, 256. 



