SCIENCE-GOSSIP. 



97 



after further treatment, is woven and sold as silk, 

 as it resembles the natural article closely and is 

 somewhat cheaper. 



Very few plants, except cotton and fiax, yield 

 simple cellulose ; in most the cellulose is combined 

 with oxygen, giving a substance known as oxycellu- 

 lose. This forms the principal part of the hard 

 tissues in the plants which fall into the Class 2 

 above. By far the greater number of plants which 

 have any hard parts consist of a still more 

 complicated substance, this is a compound of a 

 substance known as lignone with oxycellulose, 

 which, as shown above, is itself a compound of 

 cellulose. This compound is known as lignocellu- 

 lose. Jute fibre is the best example of lignocellu- 

 lose, as it is more free than ordinary woody fibre 

 from other bodies. Jute is the bast of the genus 

 Corchonis, belonging to the order Tiliaceae ; the 

 material used by gardeners for tying-up plants is 

 another example of bast fibre. 



Lignocellulose has the remarkable property of 



fixing most of the coal-tar colours ; in this it 



resembles silk and wool, and differs considerably 



from pure cellulose (cotton), which requires the use 



f some additional substance known as a mordant ; 



alum and tannin are examples of two different 

 classes of mordants. To fit woody fibre for use in 

 the manufacture of even the cheapest paper, it 

 undergoes, as a rule, two processes at least — first 

 bleaching, second, boiling in a strong soda solution. 

 The first process consists of acting on the pulped 

 fibre with solution of bleaching powder, this com- 

 bines with some of the noncellulose, i.e. lignone, 

 etc., causing it to be soluble in the alkaline solution 

 with which it is next treated. This has to be 

 repeated if a white pulp is desired. Pulp treated 

 in this way is the Class 3 mentioned in the 

 beginning of this article. For the wood cellu- 

 lose mentioned in Class 2, the lignocellulose 

 has to be completely broken up, leaving an 

 oxycellulose. This is accomplished by boiling 

 in closed vessels, at a temperature above the 

 boiling point of water, with strong alkaline (soda) 

 solutions. 



We have thus seen how the three classes of 

 paper materials mentioned above are obtained. 

 As the subsequent processes which convert them 

 into paper are mostly mechanical, we will leave 

 them as pulp ready for the machines. 

 5, Denning Road, Hampstead, N.IV. 



SCIENCE AT THE NATIONAL PORTRAIT GALLERY. 



By John T. Carrington. 



{Continued from page 66.) 



Erasmus Darwin (1731-1S02). 

 T N the remarks upon the late Charles Robert 

 Darwin {ante p. 2), mention was made of his 

 ancestor Erasmus, who was 

 born at Elston Hall, in 

 Nottinghamshire, on Decem- 

 ber i2th, 1731. At the age 

 of ten years, Erasmus was 

 sent to school at Chesterfield, 

 and nine years later he was 

 entered at St. John's College, 

 Cambridge. In 1754 he 

 graduated B.A., and came 

 out first of the junior optimes. 

 In the autumn of that year 

 Erasmus Darwin commenced 

 the study of medicine at 

 Edinburgh, and in the follow- 

 ing year he took his M.B. 

 degree at Cambridge. In 1756 

 we hear of Erasmus settling 

 at Nottingham as a physician 



but, as may be well imagined, on account of his 

 youth, he found an absence of patients. In the 

 following November he moved to Lichfield, which 

 city provided not only patients, but high reputa- 







Erasmus Darwin 



tion. At Lichfield when he found opportunity, 

 Erasmus worked steadily at the study of Botany. 

 This pursuit and his profession brought him in 

 contact with many well- 

 known men of his time. With 

 those of his neighbourhood 

 he formed a small society for 

 general scientific intercourse, 

 the meetings being held at 

 each others houses, and 

 affectionately termed by 

 Erasmus, " our lunar meet- 

 ings." Among the local men 

 of the period who formed 

 this association, were Watt, 

 Wedgewood, the Sewards 

 and others. Darwin fully 

 held his own place at these 

 meetings, being clever and 

 an excellent talker, though 

 occasionally a bad stammerer. 

 His great freedom of thought 

 and expression formed enemies as well as friends, 

 and among the former was Dr. Johnson, who was as 

 cordially hated in return by Darwin, he being 

 thorough in this as in all else he undertook. He was 



