HYDROGRAPHY IN PASSAMAQVODDY BAY 297 



SESSIONAL PAPER No. 38a 



metres. Therefore, in practice, heat propagates through the water only by the move- 

 ments of the waves and currents. 



Looking over our records one can see that at the same depths in different stations, 

 the temperature gradually becomes higher as the season advances, and in the month 

 of July, at Prince station 5, we found a temperature of 4°.9 C. at 100 fathoms or 182 

 metres. 



It is an easy matter to find out the temperature of the air or of the surface water ; 

 the thermometer can be read directly as soon as the expansion or contraction of the 

 liquid in the tube is in equilibrium with its surroundings. However, it is not thus 

 when one has to measure the exact temperature of a layer of water situated at a depth 

 of a few hundred or thousand feet. Between the surface and the deep layer to be 

 examined, there may be and, as a matter of fact, there are other layers that are colder 

 or warmer. Even if the thermometer is sent down and left long enough to indicate 

 the temperature of the water at a measured depth, when it is brought up to be read, 

 the mercurial column, by going through regions of different temperatiires, will change 

 in length; it will contract, if it meets colder water and will expand if it comes in con- 

 tact with warmer regions, it is impossible, therefore, to thus get the temperature of 

 the lower regions of the sea with an ordinary thermometer. Besides, the thermometer 

 is subjected, in the lower regions, to the enormous pressure of the upper layers, that 

 of one atmosphere for every ten metres ; even if the instrument is not broken, it will be 

 crushed; the diameter of the tube getting smaller, the mercury will indicate a higher 

 temperature for the same expansion, and, therefore, the reading of the thermometer 

 will be too high. It took almost two centuries to resolve these perplexing problems. 



Without going into details about the different suggestions worked out to reach a 

 solution of the problems, suffice it to say that the best of all the thermometers that 

 have been invented so far for taking the temperature of the lower regions is the 

 Negretti-Zambra reversing thermometer; this is the one we used in our determina- 

 tions. Negretti and Zambra invented this thermometer in 1878 and it has undergone 

 no essential changes since that time. It is noteworthy to remark here that in this 

 type there is a narrowing of the tube just above the bulb and, when the thermometer 

 is placed with the bulb iwinting dovmwards, the mercury fills the tube above the nar- 

 rowing to a greater or less extent according to the temperature. If the thermometer 

 is tipped over, either by the closing of the water-bottle, as it happens with the Petter- 

 son-Nansen bottle, or while a messenger is sent down the wire, as in the case of the 

 Ekman reversing apparatus, the mercury breaks off at the narrowing and the mercury 

 which was above this point sinks down to the opposite end of the tube and fills it to 

 a certain height; a scale on the tube thus gives the temperature at the time the ther- 

 mometer was turned over: that is called the temperature in situ. The length of the 

 broken thread of merciiry varies som.ewhat in passing through water of higher or 

 lower temperature and this change is calculated when the temperature of the mercury 

 is known at the time of the reading, and this is the reason why there is always with 

 the apparatus a second ordinary thermometer that gives the reading temperature so 

 that the con-ection may be made. In order that the thermometer may be able to 

 withstand the pressure of the water, it is placed inside a strong glass tube. 



SALINITY. 



Since there is no element that is absolutely insoluble, every element is found to a 

 certain degree in sea-water. By very accurate analysis, elements which one would not 

 expect to find have been discovered in it ; common metals, such as iron, manganese and 

 zinc, as well as precious metals, like gold and silver are found in sea-water. Those 

 rarer metals, being present only in infinitesimal quantities, are not detected by the 

 ordinary methods of analysis. 



The water of the ocean evaporates, condenses and falls again upon the earth in the 

 form of rain; it washes the earth, oozes through it and by the streams and rivers is 

 carried back to where it started from. This water, coming in contact with all sorts of 



38a— 20 



