June 1st, 1887.] 



SCIENTIFIC NEWS. 



75 



note will be detected. Even with the best possible imita- 

 tion, the shape and position of the letters, and many other 

 little details will always have small differences, and in the 

 stereoscope they can be seen distinctly. There is also this 

 further advantage, that although the imitator may find out 

 flaws in the false note he has made, he is not in the least 

 helped to find means of correcting his mistakes, or of 

 making his productions more perfect. This method can 

 also be used for testing bills of exchange, share certificates, 

 old prints, and many other objects of value. 



The Perception of Colours. — Recently in America, a 

 man claimed damages for an alleged loss of sight in his left 

 eye, owing to an accident. The eye had a thoroughly 

 healthy appearance, and an oculist who examined it pro- 

 nounced it to be perfectly sound. To prove this he made 

 the following test, which is based on the fact when green 

 and red rays are mixed they give black. Some words were 

 written in green ink on a black card, and the man who 

 said that his sight was injured was made to look through 

 spectacles, in which the right-hand glass was red and the 

 left glass was plain. He was able to read what was 

 written quite clearly, and this proved his deception, because 

 with the right eye it would have been impossible to make 

 out green letters on a black ground. 



A Deep Boring. — The American Congress has recently 

 voted one hundred thousand dollars tor the purpose of 

 boring a deep hole in the earth. This hole is to be the 

 deepest yet made, and the boring will be superintended by 

 the Engineer Corps of the U.S. army. The experiment will 

 be watched with the greatest interest, not only on account 

 of the information it will yield about the structure of the 

 earth's crust, but also in connection with the more important 

 subject of tapping the earth's internal stores of heat for 

 practical purposes. 



Action of Bever.\ges on Digestion. — Dr. James W. 

 Eraser has lately published the results of an interesting 

 series of experiments on the influence of some of our 

 common beverages on digestion. From these it appears 

 that tea, coffee, and cocoa retard digestion and the absorp- 

 tion of nitrogenised principles when peptic and pancreatic 

 digestion are taken together, and that none of them compare 

 advantageously with water as a standard beverage for ex- 

 perimental investigations. The results, of course, leave out 

 of consideration individual variations of human digestion 

 and the influence ot the glands which prepare the gastric 

 and other juices, but, after summarising his observations. 

 Dr. Eraser has been able to deduce certain rules, from which 

 we have made the following notes : — i. It is better not to 

 eat albuminoid food-stuffs at the same time as infused 

 beverages are taken ; absorption may be more rapid, but 

 there will be a loss of nutritive substance. 2. The diges- 

 tion of starchy food is assisted by tea and coft'ee. 3. Bread 

 is the natural accompaniment of tea and cocoa. 4. The 



digestion of meat is not much retarded by coffee, and it is 

 suggested that perhaps this is the reason why it is usually 

 drunk at breakfast in this country, as this meal usually con- 

 sists largely of meat, or of eggs and salt meats, the diges- 

 tion of which is not much retarded by coffee. 5. Eggs are 

 the best form of animal food to be taken with infused 

 beverages. 6. The butter used with bread undergoes diges- 

 tion more slowly in presence ot tea, and probably more 

 quickly in presence of coffee or cocoa. 



Liquid Carbonic Acid. — From Industries we learn that 

 a company formed in Berlin for the manufacture of liquid 

 carbonic acid, which is fast becoming an important industry 

 in that town, is manufacturing daily over half a ton of this 

 acid. It is sent out in steel bottles, each containing from 

 seventeen to eighteen pounds, and the price charged is 

 slightly under one shilling per pound. When the acid 

 contained in one of these bottles is expanded into gas it 

 occupies over 10,000 cubic feet. It is chiefly used for beer 

 engines and in the manufacture of mineral waters. In the 

 year 1879 Dr. Raydt, of Hanover, suggested that carbonic 

 acid could be utilized for the raising of wrecks, and 

 demonstrated the possibility ot this by an experiment at 

 Kiel. The apparatus consisted of a steel bottle containing 

 the liquid acid and a collapsed canvas bag placed over the 

 neck of the bottle. This apparatus is submerged and at- 

 tached to the object to be raised ; a cock is opened, and the 

 liquid in the bottle allowed to expand in the bag, which 

 becomes inflated and is thus caused to rise. Another ap- 

 plication introduced by Herr Krupp, of Essen, is for com- 

 pressing steel. 



Micro-Organisms in the Air. — In the interesting paper 

 read by Dr. Percy Erankland at the Society of Arts, on the 

 subject of atmospheric micro-organisms, he pointed out that 

 Koch's introduction of solid cultivating media had greatly 

 facilitated these investigations. He had also largely used 

 Hesse's glass tube, coated internally with sterile gelatine 

 peptone, through which a given quantity of air can be drawn 

 by aspiration. The estimation of the abundance of microbes 

 in the air is made by enumerating the number of colonies 

 obtained in a given quantity (ten litres) of air, and the fol- 

 lowing results were obtained. On the roof of the Science 

 Schools at South Kensington, the average number of colonies 

 varied from four in the month of January to 105 in August. 

 On the top of Primrose Hill in May the average number 

 was 9 ; at the foot of the hill it was 24 ; at St. Paul's Cathe- 

 dral the average was 1 1 in the Golden Gallery and 70 in the 

 Churchyard. The air contained much fewer microbes in 

 country places than in towns, there being, for instance, no 

 less than 554 in ten litres in the Exhibition Road, when 

 crowded, on June 8th, 1886. Dr. Erankland stated that the 

 air in a hospital ward, provided it is undisturbed, contains 

 very few organisms, and his investigation shows the import- 

 ance of preventing aerial commotion during surgical opera- 

 tions, and of removing dust in a moist condition. 



