858 



THE POPULAR SCIENCE MONTHLY. 



parasitic bodies were found in the blood 

 only at certain times, a little before and at 

 the moment of the accession of the fever ; 

 and they rapidly disappeared under the in- 

 fluence of a quinine treatment. The ad- 

 dition of a minute quantity of a dilute 

 solution of sulphate of quinine to a drop 

 of blood sufficed to destroy the organisms. 

 Mr. Laverau believes that the absence of 

 the organisms in most of the cases (only 

 twelve in the whole one hundred and ninety- 

 two) in which he failed to find them was 

 due to the patients having undergone a 

 course of treatment with quinine. 



The Freezing of a Salt Lake. Dr. Wo- 



eikoff has published the results of some 

 observations which were made at his sug- 

 gestion into the conditions of freezing and 

 thawing of a salt lake near Orenburg, 

 Russia. The lake has a surface of 473 

 square metres and is about five feet deep. 

 Its water contains sixteen per cent of salt, 

 and the mud of its bottom is rich in sul- 

 phuretted hydrogen. During January, 1S79, 

 except for one day, when the temperature 

 was barely above the freezing-point, the 

 thermometer in the air ranged from 6*3 

 to 28 - 2 centigrade, while the tempera- 

 ture of the water at the surface was from 

 3-4 to 13 C, and at the bottom from 

 -3-8 to 12-8 C. On the 27th of De- 

 cember, when the temperature of the air 

 was as low as 21 C, the lake was covered 

 with a viscous ice, which soon began to 

 thaw, however, when the temperature of the 

 air rose to 6 C, and the temperature of 

 the water was as low as 7"8 C. By the 3d 

 of January all the ice had disappeared, but 

 the temperature of the water was still 7'2 C. 

 below the freezing-point, or about 19Fahr. 

 On January 11th, the temperature of the 

 air being 22 C, and that of the water 

 being 9*8 C. at the surface and 5'6 

 at the bottom, the lake began again to be 

 covered with viscous ice, and soon froze, 

 the ice reaching a thickness of about six 

 inches in ten days. But the remainder of 

 the water was still unfrozen, notwithstand- 

 ing that its temperature decreased to 10 

 C. on January 1 7th, and even to 12 - 8 C. 

 on January 30th. Never before, says Dr. 

 Wocikoff, were temperatures below 4 C. 

 or 24"8 Fahr. observed in saline solutions 



outside of laboratories, while here were 

 temperatures of 13 C, or 8'6 Fahr., 

 observed in a salt lake. However, former 

 experiments, especially those of M. Zop- 

 piitz, have proved that there is no diffusion 

 of salt before congelation ; it seems that in 

 this lake (Kupalnoze) there is such a diffu- 

 sion of salt toward the lower stratum of 

 water, even before the freezing begins, oth- 

 erwise it would be difficult to explain how 

 colder water might remain on the surface, 

 were it not for the greater amount of salt 

 in the lower strata. It has always' been 

 difficult to explain how ice is formed on the 

 surface of oceans while the temperature of 

 maximum density is lower than that of con- 

 gelation, and the observations on this lake 

 were instituted in the hope that they might 

 throw light upon the subject. The lake, 

 however, contains too much salt to afford a 

 sure standard of comparison with oceanic 

 water. 



A Collection of Quaint Scientific Instru- 

 ments. The Royal Mathematical and Phys- 

 ical Museum, in Dresden, Saxony, was 

 founded by Prince Augustus I in the six- 

 teenth century, and has grown into an ex- 

 tensive collection of articles illustrating the 

 condition of science at particular periods, 

 and its progress. " According to Adam 

 Ries," a German expression to denote that 

 any fact is mathematically exact, refers to 

 the mathematician, Adam Ries, who in 1550 

 published a little book on reckoning with 

 counters and with the Arabic numerals. 

 His counters, and the hand-circles, staffs, and 

 various devices with which people made their 

 calculations before the Arabic numerals came 

 into general use, are shown here. Another 

 curious instrument, of the eighteenth cen- 

 tury, is a proportion staff " for the mechan- 

 ical extraction of the square and cube roots, 

 and the proportioning and calculation of 

 geometrical figuies." Among the optical 

 instruments is the famous burning mirror 

 of Walter von Tschirnhausen, of which the 

 "Acta Erudita " from 1687 to 1C97 says, 

 " He has with this glass set fire to wet wood 

 in an instant, boiled water in a small ves- 

 sel, melted lead, bored through iron plates, 

 changed brick and stone to glass." Tschirn- 

 hausen performed the first experiments on 

 solubility of the earths with this instrument. 



